python基础知识2——基本的数据类型——整型，长整型，浮点型，字符串

磨人的小妖精们啊！终于可以归置下自己的大脑啦，在这里我要把——整型，长整型，浮点型，字符串，列表，元组，字典，集合，这几个知识点特别多的东西，统一的捯饬捯饬，不然一直脑袋里面乱乱的。

对于Python，一切事物都是对象，对象基于类创建

所以，以下这些值都是对象： "wupeiqi"、38、['北京', '上海', '深圳']，并且是根据不同的类生成的对象。

官方的解释是这样的：对象是对客观事物的抽象，类是对对象的抽象。

　　因此str是类，int是类，dict、list、tuple等等都是类，但是str却不能直接使用，因为它是抽象的表示了字符串这一类事物，并不能满足表示某个特定字符串的需求，我们必须要str1 = ''初始化一个对象，这时的str1具有str的属性，可以使用str中的方法。

　　类为我们创建对象，提供功能，在python中，一切事物都是对象！（瞧，谁还敢嫌弃我们程序员没有对象，我们可以new一个呀！）

在这里介绍些类、对象、方法的查看方式：

1 >>> str1='zhenghao'
2 >>> type(str1)
3 <type 'str'>
4 >>>

查看类的所有方法：dir(类名)，就打印出了所有的类方法。

>>> dir(str)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

那么问题来了，方法名为什么有的两边带着下划线，有的没有呢？那是python用来标识私有方法、非私有方法哒，带下划线的标识私有方法，他们通常拥有不止一种调用方法。如下，我定义了两个字符串，__add__的+的效果是相同的。这里有一个内置方法很特殊：__init__，它是类中的构造方法，会在调用其所在类的时候自动执行。

1 >>> str1='zhenghao'
2 >>> str2='love xiaokai'
3 >>> str1.__add__(str2)
4 'zhenghaolove xiaokai'
5 >>> str1+str2
6 'zhenghaolove xiaokai'
7 >>>

在python中，还有一个“help(类名)”方法：可以查看类的详细功能；“help(类名.功能名)”：查看类中某功能的详细情况

一、整数

整数是不可变的，不可迭代的

1.全部的方法

1 >>> dir(int)
2 ['__abs__', '__add__', '__and__', '__clas s__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__', '__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__', '__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real']

每一个整数都具备如下功能：

  1 class int(object):
  2     """
  3     int(x=0) -> int or long
  4     int(x, base=10) -> int or long
  5     
  6     Convert a number or string to an integer, or return 0 if no arguments
  7     are given.  If x is floating point, the conversion truncates towards zero.
  8     If x is outside the integer range, the function returns a long instead.
  9     
 10     If x is not a number or if base is given, then x must be a string or
 11     Unicode object representing an integer literal in the given base.  The
 12     literal can be preceded by '+' or '-' and be surrounded by whitespace.
 13     The base defaults to 10.  Valid bases are 0 and 2-36.  Base 0 means to
 14     interpret the base from the string as an integer literal.
 15     >>> int('0b100', base=0)
 16     4
 17     """
 18     def bit_length(self): # real signature unknown; restored from __doc__
 19         """返回表示该数字时所用的最小位数
 20         int.bit_length() -> int
 21         
 22         Number of bits necessary to represent self in binary.
 23         >>> bin(37)
 24         '0b100101'
 25         >>> (37).bit_length()
 26         6
 27         """
 28         return 0
 29 
 30     def conjugate(self, *args, **kwargs): # real signature unknown
 31         """返回一个复数的共轭复数
 32          Returns self, the complex conjugate of any int. """
 33         pass
 34 
 35     def __abs__(self): # real signature unknown; restored from __doc__
 36         """ 返回绝对值
 37         x.__abs__() <==> abs(x) """
 38         pass
 39 
 40     def __add__(self, y): # real signature unknown; restored from __doc__
 41         """ 返回两个数的和
 42         x.__add__(y) <==> x+y """
 43         pass
 44 
 45     def __and__(self, y): # real signature unknown; restored from __doc__
 46         """ 返回两个数按位与的结果
 47         x.__and__(y) <==> x&y """
 48         pass
 49 
 50     def __cmp__(self, y): # real signature unknown; restored from __doc__
 51         """返回两个数比较的结果，参数从左至右（a，b），a>b返回1，a<b返回-1，a=b返回0
 52         x.__cmp__(y) <==> cmp(x,y) """
 53         pass
 54 
 55     def __coerce__(self, y): # real signature unknown; restored from __doc__
 56         """a.__coerce__(b),强制返回一个元组（a，b）
 57         x.__coerce__(y) <==> coerce(x, y) """
 58         pass
 59 
 60     def __divmod__(self, y): # real signature unknown; restored from __doc__
 61         """ 相除，得到商和余数组成的元组
 62         x.__divmod__(y) <==> divmod(x, y) """
 63         pass
 64 
 65     def __div__(self, y): # real signature unknown; restored from __doc__
 66         """返回两数相除的商 
 67         x.__div__(y) <==> x/y """
 68         pass
 69 
 70     def __float__(self): # real signature unknown; restored from __doc__
 71         """将数据类型强制转换为float
 72         x.__float__() <==> float(x) """
 73         pass
 74 
 75     def __floordiv__(self, y): # real signature unknown; restored from __doc__
 76         """ 不保留小数点后的小数除法,也可以用‘//’来表示：a//b，我们亲切地称之为“地板除”！！！
 77         x.__floordiv__(y) <==> x//y """
 78         pass
 79 
 80     def __format__(self, *args, **kwargs): # real signature unknown
 81         """ 格式化"""
 82         pass
 83 
 84     def __getattribute__(self, name): # real signature unknown; restored from __doc__
 85         """无条件被调用，通过实例访问属性 
 86         x.__getattribute__('name') <==> x.name """
 87         pass
 88 
 89     def __getnewargs__(self, *args, **kwargs): # real signature unknown
 90         """ 内部调用 __new__方法或创建对象时传入参数使用 """ 
 91         pass
 92 
 93     def __hash__(self): # real signature unknown; restored from __doc__
 94         """ 如果对象object为哈希表类型，返回对象object的哈希值。哈希值为整数。在字典查找中，哈希值用于快速比较字典的键。两个数值如果相等，则哈希值也相等   
 95         x.__hash__() <==> hash(x) """
 96         pass
 97 
 98     def __hex__(self): # real signature unknown; restored from __doc__
 99         """ 返回当前数的 十六进制 表示  
100         x.__hex__() <==> hex(x) """
101         pass
102 
103     def __index__(self): # real signature unknown; restored from __doc__
104         """ 用于切片，对数字无意义
105         x[y:z] <==> x[y.__index__():z.__index__()] """
106         pass
107 
108     def __init__(self, x, base=10): # known special case of int.__init__
109         """构造函数
110         int(x=0) -> int or long
111         int(x, base=10) -> int or long
112         
113         Convert a number or string to an integer, or return 0 if no arguments
114         are given.  If x is floating point, the conversion truncates towards zero.
115         If x is outside the integer range, the function returns a long instead.
116         
117         If x is not a number or if base is given, then x must be a string or
118         Unicode object representing an integer literal in the given base.  The
119         literal can be preceded by '+' or '-' and be surrounded by whitespace.
120         The base defaults to 10.  Valid bases are 0 and 2-36.  Base 0 means to
121         interpret the base from the string as an integer literal.
122         >>> int('0b100', base=0)
123         4
124         # (copied from class doc)
125         """
126         pass
127 
128     def __int__(self): # real signature unknown; restored from __doc__
129         """ 转换为整数
130         x.__int__() <==> int(x) """
131         pass
132 
133     def __invert__(self): # real signature unknown; restored from __doc__
134         """按位求反
135         x.__invert__() <==> ~x """
136         pass
137 
138     def __long__(self): # real signature unknown; restored from __doc__
139         """转换为长整数
140         x.__long__() <==> long(x) """
141         pass
142 
143     def __lshift__(self, y): # real signature unknown; restored from __doc__
144         """ 左移，相对二进制的操作
145         x.__lshift__(y) <==> x<<y """
146         pass
147 
148     def __mod__(self, y): # real signature unknown; restored from __doc__
149         """ 取余
150         x.__mod__(y) <==> x%y """
151         pass
152 
153     def __mul__(self, y): # real signature unknown; restored from __doc__
154         """ 返回两数相乘的积
155         x.__mul__(y) <==> x*y """
156         pass
157 
158     def __neg__(self): # real signature unknown; restored from __doc__
159         """ 返回一个数的负数，个人觉得和相反数没差
160         x.__neg__() <==> -x """
161         pass
162 
163     @staticmethod # known case of __new__
164     def __new__(S, *more): # real signature unknown; restored from __doc__
165         """ 创建一个int类的新对象
166         T.__new__(S, ...) -> a new object with type S, a subtype of T """
167         pass
168 
169     def __nonzero__(self): # real signature unknown; restored from __doc__
170         """ 判断一个数是不是0
171         x.__nonzero__() <==> x != 0 """
172         pass
173 
174     def __oct__(self): # real signature unknown; restored from __doc__
175         """ 返回该值的 八进制 表示
176         x.__oct__() <==> oct(x) """
177         pass
178 
179     def __or__(self, y): # real signature unknown; restored from __doc__
180         """ 位运算，或，针对二进制数
181         x.__or__(y) <==> x|y """
182         pass
183 
184     def __pos__(self): # real signature unknown; restored from __doc__
185         """ 并没什么卵用，说是a.__pos__()，会返回一个+a，但是不管输入整数还是负数，返回值都是他本身，感觉歪果仁真有幽默感
186         x.__pos__() <==> +x """
187         pass
188 
189     def __pow__(self, y, z=None): # real signature unknown; restored from __doc__
190         """  幂，次方
191         x.__pow__(y[, z]) <==> pow(x, y[, z]) """
192         pass
193 
194     def __radd__(self, y): # real signature unknown; restored from __doc__
195         """x.__radd__(y) <==> y+x """
196         pass
197 
198     def __rand__(self, y): # real signature unknown; restored from __doc__
199         """x.__rand__(y) <==> y&x """
200         pass
201 
202     def __rdivmod__(self, y): # real signature unknown; restored from __doc__
203         """ x.__rdivmod__(y) <==> divmod(y, x) """
204         pass
205 
206     def __rdiv__(self, y): # real signature unknown; restored from __doc__
207         """ x.__rdiv__(y) <==> y/x """
208         pass
209 
210     def __repr__(self): # real signature unknown; restored from __doc__
211         """ 转化为解释器可读取的形式
212         x.__repr__() <==> repr(x) """
213         pass
214 
215     def __rfloordiv__(self, y): # real signature unknown; restored from __doc__
216         """
217         x.__rfloordiv__(y) <==> y//x """
218         pass
219 
220     def __rlshift__(self, y): # real signature unknown; restored from __doc__
221         """ x.__rlshift__(y) <==> y<<x """
222         pass
223 
224     def __rmod__(self, y): # real signature unknown; restored from __doc__
225         """ x.__rmod__(y) <==> y%x """
226         pass
227 
228     def __rmul__(self, y): # real signature unknown; restored from __doc__
229         """ x.__rmul__(y) <==> y*x """
230         pass
231 
232     def __ror__(self, y): # real signature unknown; restored from __doc__
233         """ x.__ror__(y) <==> y|x """
234         pass
235 
236     def __rpow__(self, x, z=None): # real signature unknown; restored from __doc__
237         """ y.__rpow__(x[, z]) <==> pow(x, y[, z]) """
238         pass
239 
240     def __rrshift__(self, y): # real signature unknown; restored from __doc__
241         """ x.__rrshift__(y) <==> y>>x """
242         pass
243 
244     def __rshift__(self, y): # real signature unknown; restored from __doc__
245         """ x.__rshift__(y) <==> x>>y """
246         pass
247 
248     def __rsub__(self, y): # real signature unknown; restored from __doc__
249         """ x.__rsub__(y) <==> y-x """
250         pass
251 
252     def __rtruediv__(self, y): # real signature unknown; restored from __doc__
253         """ x.__rtruediv__(y) <==> y/x """
254         pass
255 
256     def __rxor__(self, y): # real signature unknown; restored from __doc__
257         """ x.__rxor__(y) <==> y^x """
258         pass
259 
260     def __str__(self): # real signature unknown; restored from __doc__
261         """ 转换为人阅读的形式，如果没有适于人阅读的解释形式的话，则返回解释器课阅读的形式
262         x.__str__() <==> str(x) """
263         pass
264 
265     def __sub__(self, y): # real signature unknown; restored from __doc__
266         """ 返回两数相减的差
267         x.__sub__(y) <==> x-y """
268         pass
269 
270     def __truediv__(self, y): # real signature unknown; restored from __doc__
271         """返回两数相除的商，这里的除是精确的除法，不会省略小数点后的值
272         x.__truediv__(y) <==> x/y """
273         pass
274 
275     def __trunc__(self, *args, **kwargs): # real signature unknown
276         """返回数值被截取为整形的值，在整形中无意义 
277        Truncating an Integral returns itself. """
278         pass
279 
280     def __xor__(self, y): # real signature unknown; restored from __doc__
281         """ 按位异或
282         x.__xor__(y) <==> x^y """
283         pass
284 
285     denominator = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
286      """ 分母 = 1 """   
287      """the denominator of a rational number in lowest terms"""
288 
289     imag = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
290     """ 虚数，无意义 """
291     """the imaginary part of a complex number"""
292 
293     numerator = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
294     """ 分子 = 数字大小 """
295     """the numerator of a rational number in lowest terms"""
296 
297     real = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
298     """ 实数，无意义 """
299     """the real part of a complex number"""                                                      
300 
301 int Code

help(int)

我已经在源码中加入了注释，原谅我后面很多函数没有加注释都，因为那些前面在前面已近出现过了，只是在前面多了一个'r'的，比如and，变成了rand，在这里统一总结，就是参数的顺序从右到左反过来了。比如原本的a.__div__(b)是a/b，但是a.__rdiv__(b)的表示的就是b/a，对！就是这么坑爹！

2.常用方法

在int类中，比较普通的就是+，-，*，/，%，位运算，进制间以及数据类型间的转换。下面对于比较特别但是常用的方法再进行一下记录：

（1） __cmp__:比较两个数的大小

1 >>> a = 12
2 >>> b = 15
3 >>> cmp(a,b)         #比较两个参数的值，如果第一个参数小于第二个参数，返回-1
4 -1
5 >>> cmp(b,a)         #比较两个参数的值，如果第一个参数大于第二个参数，返回1
6 1
7 >>> c = 12    
8 >>> a.__cmp__(c)     #比较两个参数的值，如果第一个参数等于第二个参数，返回0   
9 0                    #cmp方法也有两种调用方式

（2）__neg__/__abs__:取相反数/取绝对值

 1 >>> a = -12
 2 >>> b = 21
 3 >>> a.__neg__() #求相反数
 4 12
 5 >>> b.__neg__()
 6 -21
 7 >>> a.__abs__() #求绝对值
 8 12
 9 >>> b.__abs__()
10 21

（3）__coerce__:强制返回一个元组（好吧，我承认这个并不常用，就是和divmod比较看看）

（4）__divmod__:返回两个数相除的商和余数组成的元组（商，余数）　　　　　　　　应用:显示数据分页

1 >>> a = 102
2 >>> b = 10
3 >>> a.__divmod__(b)
4 (10, 2)
5 >>> a.__coerce__(b)
6 (102, 10)

（5）__floordiv__:不保留小数点后的小数除法，在这儿把所有的除法都整理了，然而我并没发现__div__和__floordiv__的区别啊~~~　　　　　　

 1 >>> a = 13
 2 >>> b = 2
 3 >>> a.__div__(b)
 4 6
 5 >>> a.__truediv__(b)
 6 6.5
 7 >>> a.__floordiv__(b)
 8 6
 9 >>> a/b
10 6
11 >>> a//b
12 6

（6）__repr__/__str__:转化为解释器可读取的形式/转换为人阅读的形式

二、长整型

可能如：2147483649、9223372036854775807

1 >>> dir(long)
2 ['__abs__', '__add__', '__and__', '__class__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__', '__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__', '__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real']

每个长整型都具备如下功能：

long

长整形就是长长的整形。。。现在的操作系统大部分int类型的表示范围是2^32,而长整形就是2^64，在python里，不需要程序员手动的转换int和long的数据类型，当数值的大小超过了int的表示范围，python会自动将数据类型转换为long型，就是这么智能！！！既然long和int同表示整形，那么他们包含的方法也是差不多的，在这里就不再介绍了。

三、浮点型

如：3.14、2.88

1 >>> dir(float)
2 ['__abs__', '__add__', '__class__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__eq__', '__float__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getformat__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__int__', '__le__', '__long__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__nonzero__', '__pos__', '__pow__', '__radd__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rmod__', '__rmul__', '__rpow__', '__rsub__', '__rtruediv__', '__setattr__', '__setformat__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', 'as_integer_ratio', 'conjugate', 'fromhex', 'hex', 'imag', 'is_integer', 'real']

每个浮点型都具备如下功能：

float

我们在创建对象的时候，python也会很聪明的识别出float类型，在计算的时候也是这样，不管表达式中有多少整形多少浮点型，只要存在浮点型，那么所有计算都按照浮点型计算，得出的结果也会是float类型。其余方法和整形并没有太大差别，在这里也不做详细总结了。

四、字符串

字符串是不可修改不可变的，有序的，不可迭代的，有索引和切片

1.字符串全部方法

如：'zhenghao'、‘xiaokai'

1 >> dir(str)
2 ['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

每个字符串都具备如下功能：

  1 class str(basestring):
  2     """
  3     str(object='') -> string
  4     
  5     Return a nice string representation of the object.
  6     If the argument is a string, the return value is the same object.
  7     """
  8     def capitalize(self):  
  9         """ 首字母变大写 """
 10         """
 11         S.capitalize() -> string
 12         
 13         Return a copy of the string S with only its first character
 14         capitalized.
 15         """
 16         return ""
 17 
 18     def center(self, width, fillchar=None):  
 19         """ 内容居中，width：总长度；fillchar：空白处填充内容，默认无 """
 20         """
 21         S.center(width[, fillchar]) -> string
 22         
 23         Return S centered in a string of length width. Padding is
 24         done using the specified fill character (default is a space)
 25         """
 26         return ""
 27 
 28     def count(self, sub, start=None, end=None):  
 29         """ 子序列个数 """
 30         """
 31         S.count(sub[, start[, end]]) -> int
 32         
 33         Return the number of non-overlapping occurrences of substring sub in
 34         string S[start:end].  Optional arguments start and end are interpreted
 35         as in slice notation.
 36         """
 37         return 0
 38 
 39     def decode(self, encoding=None, errors=None):  
 40         """ 解码 """
 41         """
 42         S.decode([encoding[,errors]]) -> object
 43         
 44         Decodes S using the codec registered for encoding. encoding defaults
 45         to the default encoding. errors may be given to set a different error
 46         handling scheme. Default is 'strict' meaning that encoding errors raise
 47         a UnicodeDecodeError. Other possible values are 'ignore' and 'replace'
 48         as well as any other name registered with codecs.register_error that is
 49         able to handle UnicodeDecodeErrors.
 50         """
 51         return object()
 52 
 53     def encode(self, encoding=None, errors=None):  
 54         """ 编码，针对unicode """
 55         """
 56         S.encode([encoding[,errors]]) -> object
 57         
 58         Encodes S using the codec registered for encoding. encoding defaults
 59         to the default encoding. errors may be given to set a different error
 60         handling scheme. Default is 'strict' meaning that encoding errors raise
 61         a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and
 62         'xmlcharrefreplace' as well as any other name registered with
 63         codecs.register_error that is able to handle UnicodeEncodeErrors.
 64         """
 65         return object()
 66 
 67     def endswith(self, suffix, start=None, end=None):  
 68         """ 是否以 xxx 结束 """
 69         """
 70         S.endswith(suffix[, start[, end]]) -> bool
 71         
 72         Return True if S ends with the specified suffix, False otherwise.
 73         With optional start, test S beginning at that position.
 74         With optional end, stop comparing S at that position.
 75         suffix can also be a tuple of strings to try.
 76         """
 77         return False
 78 
 79     def expandtabs(self, tabsize=None):  
 80         """ 将tab转换成空格，默认一个tab转换成8个空格 """
 81         """
 82         S.expandtabs([tabsize]) -> string
 83         
 84         Return a copy of S where all tab characters are expanded using spaces.
 85         If tabsize is not given, a tab size of 8 characters is assumed.
 86         """
 87         return ""
 88 
 89     def find(self, sub, start=None, end=None):  
 90         """ 寻找子序列位置，如果没找到，则异常 """
 91         """
 92         S.find(sub [,start [,end]]) -> int
 93         
 94         Return the lowest index in S where substring sub is found,
 95         such that sub is contained within S[start:end].  Optional
 96         arguments start and end are interpreted as in slice notation.
 97         
 98         Return -1 on failure.
 99         """
100         return 0
101 
102     def format(*args, **kwargs): # known special case of str.format
103         """ 字符串格式化，动态参数，将函数式编程时细说 """
104         """
105         S.format(*args, **kwargs) -> string
106         
107         Return a formatted version of S, using substitutions from args and kwargs.
108         The substitutions are identified by braces ('{' and '}').
109         """
110         pass
111 
112     def index(self, sub, start=None, end=None):  
113         """ 子序列位置，如果没找到，则返回-1  """
114         S.index(sub [,start [,end]]) -> int
115         
116         Like S.find() but raise ValueError when the substring is not found.
117         """
118         return 0
119 
120     def isalnum(self):  
121         """ 是否是字母和数字 """
122         """
123         S.isalnum() -> bool
124         
125         Return True if all characters in S are alphanumeric
126         and there is at least one character in S, False otherwise.
127         """
128         return False
129 
130     def isalpha(self):  
131         """ 是否是字母 """
132         """
133         S.isalpha() -> bool
134         
135         Return True if all characters in S are alphabetic
136         and there is at least one character in S, False otherwise.
137         """
138         return False
139 
140     def isdigit(self):  
141         """ 是否是数字 """
142         """
143         S.isdigit() -> bool
144         
145         Return True if all characters in S are digits
146         and there is at least one character in S, False otherwise.
147         """
148         return False
149 
150     def islower(self):  
151         """ 是否小写 """
152         """
153         S.islower() -> bool
154         
155         Return True if all cased characters in S are lowercase and there is
156         at least one cased character in S, False otherwise.
157         """
158         return False
159 
160     def isspace(self):  
161         """是否空格
162         S.isspace() -> bool
163         
164         Return True if all characters in S are whitespace
165         and there is at least one character in S, False otherwise.
166         """
167         return False
168 
169     def istitle(self):  
170         """是否标题
171         S.istitle() -> bool
172         
173         Return True if S is a titlecased string and there is at least one
174         character in S, i.e. uppercase characters may only follow uncased
175         characters and lowercase characters only cased ones. Return False
176         otherwise.
177         """
178         return False
179 
180     def isupper(self):  
181         """是否大写
182         S.isupper() -> bool
183         
184         Return True if all cased characters in S are uppercase and there is
185         at least one cased character in S, False otherwise.
186         """
187         return False
188 
189     def join(self, iterable):  
190         """ 连接 """
191         """
192         S.join(iterable) -> string
193         
194         Return a string which is the concatenation of the strings in the
195         iterable.  The separator between elements is S.
196         """
197         return ""
198 
199     def ljust(self, width, fillchar=None):  
200         """ 内容左对齐，右侧填充 """
201         """
202         S.ljust(width[, fillchar]) -> string
203         
204         Return S left-justified in a string of length width. Padding is
205         done using the specified fill character (default is a space).
206         """
207         return ""
208 
209     def lower(self):  
210         """ 变小写 """
211         """
212         S.lower() -> string
213         
214         Return a copy of the string S converted to lowercase.
215         """
216         return ""
217 
218     def lstrip(self, chars=None):  
219         """ 移除左侧空白 """
220         """
221         S.lstrip([chars]) -> string or unicode
222         
223         Return a copy of the string S with leading whitespace removed.
224         If chars is given and not None, remove characters in chars instead.
225         If chars is unicode, S will be converted to unicode before stripping
226         """
227         return ""
228 
229     def partition(self, sep):  
230         """ 分割，前，中，后三部分 """
231         """
232         S.partition(sep) -> (head, sep, tail)
233         
234         Search for the separator sep in S, and return the part before it,
235         the separator itself, and the part after it.  If the separator is not
236         found, return S and two empty strings.
237         """
238         pass
239 
240     def replace(self, old, new, count=None):  
241         """ 替换 """
242         """
243         S.replace(old, new[, count]) -> string
244         
245         Return a copy of string S with all occurrences of substring
246         old replaced by new.  If the optional argument count is
247         given, only the first count occurrences are replaced.
248         """
249         return ""
250 
251     def rfind(self, sub, start=None, end=None):  
252         """
253         S.rfind(sub [,start [,end]]) -> int
254         
255         Return the highest index in S where substring sub is found,
256         such that sub is contained within S[start:end].  Optional
257         arguments start and end are interpreted as in slice notation.
258         
259         Return -1 on failure.
260         """
261         return 0
262 
263     def rindex(self, sub, start=None, end=None):  
264         """
265         S.rindex(sub [,start [,end]]) -> int
266         
267         Like S.rfind() but raise ValueError when the substring is not found.
268         """
269         return 0
270 
271     def rjust(self, width, fillchar=None):  
272         """
273         S.rjust(width[, fillchar]) -> string
274         
275         Return S right-justified in a string of length width. Padding is
276         done using the specified fill character (default is a space)
277         """
278         return ""
279 
280     def rpartition(self, sep):  
281         """
282         S.rpartition(sep) -> (head, sep, tail)
283         
284         Search for the separator sep in S, starting at the end of S, and return
285         the part before it, the separator itself, and the part after it.  If the
286         separator is not found, return two empty strings and S.
287         """
288         pass
289 
290     def rsplit(self, sep=None, maxsplit=None):  
291         """
292         S.rsplit([sep [,maxsplit]]) -> list of strings
293         
294         Return a list of the words in the string S, using sep as the
295         delimiter string, starting at the end of the string and working
296         to the front.  If maxsplit is given, at most maxsplit splits are
297         done. If sep is not specified or is None, any whitespace string
298         is a separator.
299         """
300         return []
301 
302     def rstrip(self, chars=None):  
303         """
304         S.rstrip([chars]) -> string or unicode
305         
306         Return a copy of the string S with trailing whitespace removed.
307         If chars is given and not None, remove characters in chars instead.
308         If chars is unicode, S will be converted to unicode before stripping
309         """
310         return ""
311 
312     def split(self, sep=None, maxsplit=None):  
313         """ 分割， maxsplit最多分割几次 """
314         """
315         S.split([sep [,maxsplit]]) -> list of strings
316         
317         Return a list of the words in the string S, using sep as the
318         delimiter string.  If maxsplit is given, at most maxsplit
319         splits are done. If sep is not specified or is None, any
320         whitespace string is a separator and empty strings are removed
321         from the result.
322         """
323         return []
324 
325     def splitlines(self, keepends=False):  
326         """ 根据换行分割 """
327         """
328         S.splitlines(keepends=False) -> list of strings
329         
330         Return a list of the lines in S, breaking at line boundaries.
331         Line breaks are not included in the resulting list unless keepends
332         is given and true.
333         """
334         return []
335 
336     def startswith(self, prefix, start=None, end=None):  
337         """ 是否起始 """
338         """
339         S.startswith(prefix[, start[, end]]) -> bool
340         
341         Return True if S starts with the specified prefix, False otherwise.
342         With optional start, test S beginning at that position.
343         With optional end, stop comparing S at that position.
344         prefix can also be a tuple of strings to try.
345         """
346         return False
347 
348     def strip(self, chars=None):  
349         """ 移除两段空白 """
350         """
351         S.strip([chars]) -> string or unicode
352         
353         Return a copy of the string S with leading and trailing
354         whitespace removed.
355         If chars is given and not None, remove characters in chars instead.
356         If chars is unicode, S will be converted to unicode before stripping
357         """
358         return ""
359 
360     def swapcase(self):  
361         """ 大写变小写，小写变大写 """
362         """
363         S.swapcase() -> string
364         
365         Return a copy of the string S with uppercase characters
366         converted to lowercase and vice versa.
367         """
368         return ""
369 
370     def title(self):  
371         """
372         S.title() -> string
373         
374         Return a titlecased version of S, i.e. words start with uppercase
375         characters, all remaining cased characters have lowercase.
376         """
377         return ""
378 
379     def translate(self, table, deletechars=None):  
380         """
381         转换，需要先做一个对应表，最后一个表示删除字符集合
382         intab = "aeiou"
383         outtab = "12345"
384         trantab = maketrans(intab, outtab)
385         str = "this is string example....wow!!!"
386         print str.translate(trantab, 'xm')
387         """
388 
389         """
390         S.translate(table [,deletechars]) -> string
391         
392         Return a copy of the string S, where all characters occurring
393         in the optional argument deletechars are removed, and the
394         remaining characters have been mapped through the given
395         translation table, which must be a string of length 256 or None.
396         If the table argument is None, no translation is applied and
397         the operation simply removes the characters in deletechars.
398         """
399         return ""
400 
401     def upper(self):  
402         """
403         S.upper() -> string
404         
405         Return a copy of the string S converted to uppercase.
406         """
407         return ""
408 
409     def zfill(self, width):  
410         """方法返回指定长度的字符串，原字符串右对齐，前面填充0。"""
411         """
412         S.zfill(width) -> string
413         
414         Pad a numeric string S with zeros on the left, to fill a field
415         of the specified width.  The string S is never truncated.
416         """
417         return ""
418 
419     def _formatter_field_name_split(self, *args, **kwargs): # real signature unknown
420         pass
421 
422     def _formatter_parser(self, *args, **kwargs): # real signature unknown
423         pass
424 
425     def __add__(self, y):  
426         """ x.__add__(y) <==> x+y """
427         pass
428 
429     def __contains__(self, y):  
430         """ x.__contains__(y) <==> y in x """
431         pass
432 
433     def __eq__(self, y):  
434         """ x.__eq__(y) <==> x==y """
435         pass
436 
437     def __format__(self, format_spec):  
438         """
439         S.__format__(format_spec) -> string
440         
441         Return a formatted version of S as described by format_spec.
442         """
443         return ""
444 
445     def __getattribute__(self, name):  
446         """ x.__getattribute__('name') <==> x.name """
447         pass
448 
449     def __getitem__(self, y):  
450         """ x.__getitem__(y) <==> x[y] """
451         pass
452 
453     def __getnewargs__(self, *args, **kwargs): # real signature unknown
454         pass
455 
456     def __getslice__(self, i, j):  
457         """
458         x.__getslice__(i, j) <==> x[i:j]
459                    
460                    Use of negative indices is not supported.
461         """
462         pass
463 
464     def __ge__(self, y):  
465         """ x.__ge__(y) <==> x>=y """
466         pass
467 
468     def __gt__(self, y):  
469         """ x.__gt__(y) <==> x>y """
470         pass
471 
472     def __hash__(self):  
473         """ x.__hash__() <==> hash(x) """
474         pass
475 
476     def __init__(self, string=''): # known special case of str.__init__
477         """
478         str(object='') -> string
479         
480         Return a nice string representation of the object.
481         If the argument is a string, the return value is the same object.
482         # (copied from class doc)
483         """
484         pass
485 
486     def __len__(self):  
487         """ x.__len__() <==> len(x) """
488         pass
489 
490     def __le__(self, y):  
491         """ x.__le__(y) <==> x<=y """
492         pass
493 
494     def __lt__(self, y):  
495         """ x.__lt__(y) <==> x<y """
496         pass
497 
498     def __mod__(self, y):  
499         """ x.__mod__(y) <==> x%y """
500         pass
501 
502     def __mul__(self, n):  
503         """ x.__mul__(n) <==> x*n """
504         pass
505 
506     @staticmethod # known case of __new__
507     def __new__(S, *more):  
508         """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
509         pass
510 
511     def __ne__(self, y):  
512         """ x.__ne__(y) <==> x!=y """
513         pass
514 
515     def __repr__(self):  
516         """ x.__repr__() <==> repr(x) """
517         pass
518 
519     def __rmod__(self, y):  
520         """ x.__rmod__(y) <==> y%x """
521         pass
522 
523     def __rmul__(self, n):  
524         """ x.__rmul__(n) <==> n*x """
525         pass
526 
527     def __sizeof__(self):  
528         """ S.__sizeof__() -> size of S in memory, in bytes """
529         pass
530 
531     def __str__(self):  
532         """ x.__str__() <==> str(x) """
533         pass
534 
535 str
536 
537 str Code

View Code

2.字符串常用方法：

（1）capitalize：将首字母大写

1 >>> name = 'hello'
2 >>> name.capitalize()
3 'Hello'

（2）center/ljust/rjust：固定字符串长度，居中/居左/居右，下面是使用示例，当然没有正常人会上来就这么用，一般用在打印列表和字典的时候整理格式。

1 >>> str1='zhenghao love xiaokai'
2 >>> str1.center(30,'*') #设置格式左对齐，其余剩余部分由‘*’填充
3 '****zhenghao love xiaokai*****'
4 >>> str1.ljust(30, ) #设置格式左对齐，其余剩余部分由空格填充
5 'zhenghao love xiaokai         '
6 >>> str1.rjust(30,'$') #设置格式左对齐，其余剩余部分由‘$’填充
7 '$$$$$$$$$zhenghao love xiaokai'
8 >>>

（3）count：子序列个数，用来统计一个字符串中包含指定子序列的个数。这个子序列可以是一个字符，也可以是多个字符~~

1 >>> str1 = 'hello,world'
2 >>> str1.count('o')
3 2
4 >>> str1.count('he')
5 1

（4）encode/decode：编码/解码，如下左图，各个编码之间是不能直接转换的，计算机内存中默认存储的编码格式是unicode，所以当我们需要将编码在utf8和gbk之间转换的时候，都需要和unicode做操作。
　　　　我的终端编码是gbk编码的，当我创建一个string = '景'时，string就被存储成gbk格式。此时我想把gbk格式转换成utf8格式，就要先将原gbk格式的string转换成unicode格式，然后再将unicode转换成utf8格式。如下右图，老师说，把这个字整乱码了我们的目的就达到了，哈~

（5）endswith:是否以...（子串）结尾。这里的子串依然可以是一个或多个字符。

1 >>> str1 = 'hello,Have a nice day'
2 >>> str1.endswith('day')
3 True

（6）expandtabs：将tab转换成空格，默认一个tab转换成8个空格。当然这里也可以自行指定转换成多少个空格，要不是怕写不下，我就指定它转成千八百个。。。

1 >>> name = '    E'
2 >>> name.expandtabs()
3 '        E'
4 >>> name.expandtabs(20)
5 '                    E'

（7）find：返回字符串中第一个子序列的下标。

　　　　 rfind：和find用法一样，只是它是从右向左查找

　　 index：和find的左右一致，只是find找不到的时候会返回-1，而index找不到的时候会报错

　　　　值得注意的是，当我们在一个字符串中查找某一个子序列的时候，如果这个字符串中含有多个子序列，只会返回第一个找到的下标，不会返回其他的。

1 >>> name = 'hello,e,how are you'

2 >>> name.find('o')

 3 4
 4 >>> name.find('t')
 5 -1

 6 >>> name.index('e')           
 7 1
 8 >>> name.index('t')
 9 
10 Traceback (most recent call last):
11   File "<pyshell#234>", line 1, in <module>
12     name.index('t')
13 ValueError: substring not found

（8）format：各种格式化，动态参数。

（9）isalnum/isalpha/isdigit/isspace/islower/istitle/isupper:是否是字母或数字/是否字母/是否数字/是否空格/是否小写/是否标题/是否全大写，总之都是一些判断的方法，返回的不是True就是False。。。

（10）partition/split：这两个方法都用来分割。

　　partition会将指定的子串串提取并将子串两侧内容分割，只匹配一次，并返回元祖；

　　split会根据指定子串，将整个字符串所有匹配的子串匹配到并剔除，将其他内容分割，返回数组。

1 >>> food = 'apple,banana,chocolate'
2 >>> food.split(',')
3 ['apple', 'banana', 'chocolate']
4 >>> food.partition(',')
5 ('apple', ',', 'banana,chocolate')

（11）replace：替换。会替换字符串中所有符合条件的子串。。。原谅我的chinglish。。。

1 >>> str1 = 'I\'m Rita,Do you remember,Rita?'
2 >>> str1.replace('Rita','Eva')
3 "I'm Eva,Do you remember,Eva?"

（12）swapcase：大写变小写，小写变大写

1 >>> str1 = 'I\'m Eva'
2 >>> str1.swapcase()
3 "i'M eVA"

（13）translate：替换，删除字符串。这个方法的使用比较麻烦，在使用前需要引入string类，并调用其中的maketrans方法建立映射关系。这样，在translate方法中，加入映射参数，就可以看到效果了。如下‘aeiou’分别和‘12345’建立了映射关系，于是在最后，aeiou都被12345相应的替换掉了，translate第二个参数是删除，它删除了所有的‘.’

1 >>> in_tab = 'aeiou'
2 >>> out_tab = '12345'
3 >>> import string
4 >>> transtab = string.maketrans(in_tab,out_tab)
5 >>> str = 'this is a translate example...wow!'
6 >>> str1 = 'this is a translate example...wow!'
7 >>> print str1.translate(transtab,'..')
8 th3s 3s 1 tr1nsl1t2 2x1mpl2w4w!

3.字符串转义字符：

如果字符串内部既包含'又包含"怎么办？可以用转义字符\来标识，比如：

'I\'m \"OK\"!'

表示的字符串内容是：

I'm "OK"!

转义字符\可以转义很多字符，比如\n表示换行，\t表示制表符，字符\本身也要转义，所以\\表示的字符就是\，可以在Python的交互式命令行用print()打印字符串看看：

1 >>> print('I\'m ok.')
2 I'm ok.
3 >>> print('I\'m learning\nPython.')
4 I'm learning
5 Python.
6 >>> print('\\\n\\')
7 \
8 \

如果字符串里面有很多字符都需要转义，就需要加很多\，为了简化，Python还允许用r''表示''内部的字符串默认不转义，可以自己试试：

1 >>> print('\\\t\\')
2 \       \
3 >>> print(r'\\\t\\')
4 \\\t\\

如果字符串内部有很多换行，用\n写在一行里不好阅读，为了简化，Python允许用'''...'''的格式表示多行内容，可以自己试试：

1  >>> print('''line1
2 
3 ... line2
4 ... line3''')
5 line1
6 line2
7 line3

上面是在交互式命令行内输入，注意在输入多行内容时，提示符由>>>变为...，提示你可以接着上一行输入。如果写成程序，就是：

1 print('''line1
2 line2
3 line3''')

多行字符串'''...'''还可以在前面加上r使用，请自行测试。

4.字符串格式化，占位符：

在Python中，采用的格式化方式和C语言是一致的，用%实现，举例如下：

1 >>> 'Hello, %s' % 'world'
2 'Hello, world'
3 >>> 'Hi, %s, you have $%d.' % ('zh', 1000000)
4 'Hi, zh, you have $1000000.'

你可能猜到了，%运算符就是用来格式化字符串的。在字符串内部，%s表示用字符串替换，%d表示用整数替换，有几个%?占位符，后面就跟几个变量或者值，顺序要对应好。如果只有一个%?，括号可以省略。

常见的占位符有：

%d	整数
%f	浮点数
%s	字符串
%x	十六进制整数

其中，格式化整数和浮点数还可以指定是否补0和整数与小数的位数：

1 >>> '%2d-%02d' % (3, 1)
2 ' 3-01'
3 >>> '%.2f' % 3.1415926
4 '3.14'

如果你不太确定应该用什么，%s永远起作用，它会把任何数据类型转换为字符串：

1 >>> 'Age: %s. Gender: %s' % (25, True)
2 'Age: 25. Gender: True’

有些时候，字符串里面的%是一个普通字符怎么办？这个时候就需要转义，用%%来表示一个%：

1 >>> 'growth rate: %d %%' % 7
2 'growth rate: 7 %'

其实，上面这种格式化方法，常常被认为是太“古老”了。因为在 Python 中还有新的格式化方法。

1 >>> s1 = "I like {}".format("python")
2 >>> s1
3 'I like python'
4 >>> s2 = "Suzhou is more than {} years. {} lives in here.".format(2500, "qiwsir") 
5 >>> s2
6 'Suzhou is more than 2500 years. qiwsir lives in here.'

这就是 Python 非常提倡的 string.format()的格式化方法，其中 {} 作为占位符。

这种方法真的是非常好，而且非常简单，只需要将对应的东西，按照顺序在 format 后面的括号中排列好，分别对应占位符 {} 即可。我喜欢的方法。

如果你觉得还不明确，还可以这样来做。

1 >>> print "Suzhou is more than {year} years. {name} lives in here.".format(year=2500, name="qiwsir") 
2 Suzhou is more than 2500 years. qiwsir lives in here.

真的很简洁，堪称优雅。

其实，还有一种格式化的方法，被称为“字典格式化”，这里仅仅列一个例子，如果看官要了解字典的含义，本教程后续会有的。

1 >>> lang = "Python"
2 >>> print "I love %(program)s"%{"program":lang}
3 I love Python

列举了三种基本格式化的方法，你喜欢那种？我推荐：string.format()

5.字符串的索引和切片

例如这样一个字符串 Python，它就是几个字符：P,y,t,h,o,n，排列起来。这种排列是非常严格的，不仅仅是字符本身，而且还有顺序，换言之，如果某个字符换了，就编程一个新字符串了；如果这些字符顺序发生变化了，也成为了一个新字符串。在 Python 中，把像字符串这样的对象类型（后面还会冒出来类似的其它有这种特点的对象类型，比如列表），统称为序列。顾名思义，序列就是“有序排列”。

 1 >>> str='python'
 2 >>> str[0]
 3 'p'
 4 >>> str[:4]
 5 'pyth'
 6 >>> str[:]
 7 'python'
 8 >>> str[1:4]
 9 'yth'
10 >>> str[-3:-1]
11 'ho'
12 >>> str.index('t')
13 2
14 >>>

6.字符串连接

1 >>> a='三毛'
2 >>> s='荷西'
3 >>> z=a+s
4 >>> z
5 '\xe4\xb8\x89\xe6\xaf\x9b\xe8\x8d\xb7\xe8\xa5\xbf'
6 >>> print(z)
7 三毛荷西
8 >>>