python之常见列表、字典知识

今天刚整理出来列表跟字典的东西， 略慢， 以后会按照进度来更新。

upper() : #将字符串中所有小写字母转换成大写

s1 = 'i like python'

s1 = 'i like python'
print(str.upper())
I LIKE PYTHON


lower() #将字符串中所有大写转换成小写

s1 = 'I LIKE PYTHON'
print(str.lower()
i like python


strip() #移除字符串头尾指定的字符生成新字符串

s1 = '****i like python****'
print(str.strip('*'))
i like python


join  #将序列中德元素以指定的字符串链接生成一个新的字符串

s1 = "-"
s2 = ""
s3 = ("p","y","t","h","o","n")
print(s1.join(s3))
print(s2.join(s3))
p-y-t-h-o-n
python


replace   将字符串中德旧字符串替换成新字符串后生成的新字符串。

s1 = 'i like python'
print(s1.replace("i","a"))
a lake python


captlize #首字母大写，其余字母小写。

s1 = 'i like python'
print(s1.capitalize())
I like python


title #字符串中所有的单词首字母都以大写为开始，其余均为小写

s1 = 'i like python'
s2 = 'i,like,python'
s3 = 'ilikepython'
s4 = 'ilikepython'
l1 = s1.split()
l2 = s2.split(',')
l3 = s2.split('a')
l4 = s2.split('a',2)
print(l1)
print(l2)
print(l3)
print(l4)
['i', 'like', 'python']
['i', 'like', 'python']
['i,like,python']
['i,like,python']


split str--->list

s1 = 'i like python'
s2 = 'i,like,python'
s3 = 'ilikepython'
s4 = 'ilikepython'
l1 = s1.split()
l2 = s2.split(',')
l3 = s2.split('a')
l4 = s2.split('a',2)
print(l1)
print(l2)
print(l3)
print(l4)
['i', 'like', 'python']
['i', 'like', 'python']
['i,like,python']
['i,like,python']


join   list---> str

l1 = ['i', 'like', 'python']
s1 = ' '.join(l1)
print(s1,type(s1))
i like python <class 'str'>


find index 通过元素找索引

# find 找不到返回-1
# index找不到会报错
s = 'ilikepython'
s11 = s.find('l')
s12 = s.find('li')
print(s11,type(s11))
print(s12,type(s12))
s11 = s.find('i',1)
print(s11)
print(s.find('P'))
print(s.index('P'))


count 查找元素的个数

s = 'i like python'
print(s.count('i'))
2


isdigit() 检测字符串是否只由数字组成

s = 'ilikepython123'
s1 = '123456abc '
print(s.isalnum())
print(s1.isalnum())


isalpha() 检测字符串是否只由字母组成

s = 'ilikepython123'
s1 = '123456abc '
print(s.isalnum())
print(s1.isalnum())


isalpnum()

s = 'ilikepython123'
s1 = '123456abc '
print(s.isalnum())
print(s1.isalnum())


startswith endswith 判断一个文本以某个或者几个字符开始或者结束，结果以True或者False返回.

s = 'i like python'
print(s.startswith('i'))
print(s.endswith('n'))


swapcase 大小写翻转

s = 'I Like Python'
print(s.swapcase())
i lIKE pYTHON


center 设置总长度并居中

s = 'i like python'
s = s.center(30,)
s = s.center(30,'*')
print(s)

 
format

s = "我叫{}，今年{}，爱好{}"
# 第一种用法
s12 = s.format('张三', '25', '男')
print(s12)
# 第二种用法
s1 = "我叫{0}，今年{1}，爱好{2},我依然叫{0}"
s13 = s1.format('张三', '25', '男')
print(s13)
# 第三种用法
s3 = "我叫{name}，今年{age}，爱好{hobby}"
s14 = s3.format(age=25,hobby='girl',name='张三')
print(s14)


len() 测量个数

s = 'i like python'
print(len(s))


list：列表的增删改查

增
#append() 追加
s = ["i","like","python"]
s.append('abc')
s.append(1)
s.append([1,2,3])
print(s)

#insert(index, obj) 插入列表的指定位置
s.insert(1,'abc')
print(s)

#extend() 在列表末尾一次性追加另一个序列中的多个值
s.extend('abc')
s.extend(['aa','bb','cc'])
print(s)


#删
#pop 按索引删除 有返回值
s = ["i","like","python"]
print(s.pop(1))

#remove 按元素删除
s.remove('like')
print(s)

#clear 清空
s.clear()
print(s)

#del
del s     #删除列表
del s[1]  #按照索引删除
del s[:2] #按照切片删除
print(s)


#改
s = ["i","like","python","zhangsan","lisi","wangwu"]
按元素改：s[0] = '张三'
按切片改：s[1:2] = 'aa'     s[1:4:2] = 'aa'


#查
print(s)        #列出列表内容
print(s[1])     #按照索引查找
print(s[1::2])  #切片查找
for n in s:     #for循环查找
    print(n)


#dict: 字典的增删改查

python之常见列表、字典知识

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