[慕课网 Python进阶 廖雪峰]

其他 2018-06-08 16:17:25 阅读次数: 2 
# -*- coding:utf8 -*-
# 2-3 python把函数作为参数
import math
def add(x, y, f):
    return f(x) + f(y)
print add(25, 9, math.sqrt)

# 2-4 python中map()函数
def format_name(s):
    return s.title()
print map(format_name, ['adam', 'LISA', 'barT'])

# 2-5 python中reduce()函数
def prod(x, y):
    return x * y
print reduce(prod, [2, 4, 5, 7, 12])

# 2-6 python中filter()函数
# s.strip(rm) 删除 s 字符串中开头、结尾处的 rm 序列的字符。
import math
def is_sqr(x):
    return math.sqrt(x)%1 == 0
print filter(is_sqr, range(1, 101))

# 2-7 python中自定义排序函数
# 如果 x 应该排在 y 的前面，返回 -1，如果 x 应该排在 y 的后面，返回 1。如果 x 和 y 相等，返回 0。
def cmp_ignore_case(s1, s2):
    if s1.lower() < s2.lower():
        return -1
    if s1.lower() > s2.lower():
        return 1
    return 0
print sorted(['bob', 'about', 'Zoo', 'Credit'], cmp_ignore_case)

# 2-8 python中返回函数
def calc_prod(lst):
    def c_prod():
        def prod(x, y):
            return x * y
        return reduce(prod, lst)
    return c_prod
f = calc_prod([1, 2, 3, 4])
print f()

# 2-9 python中闭包
def count():
    fs = []
    for i in range(1, 4):
        def f(i):
            return lambda : i*i
        fs.append(f(i))
    return fs
f1, f2, f3 = count()
print f1(), f2(), f3()

# 2-10 python中匿名函数
print filter(lambda s:s and len(s.strip()) > 0, ['test', None, '', 'str', '  ', 'END'])

# 2-12 python中编写无参数decorator
import time
def performance(f):
    def fn(x):
        print 'call '+f.__name__+'() in '+time.strftime('%Y-%m-%d',time.localtime(time.time()))
        return f(x)
    return fn

@performance
def factorial(n):
    return reduce(lambda x,y: x*y, range(1, n+1))
print factorial(10)

# 2-13 python中编写带参数decorator
import time
def performance(unit):
    def fn(f):
        def fn1(x):
            t1 = time.time()
            t2 = time.time()
            t = (t2 - t1)*1000 if unit =='ms' else (t2 - t1)
            print 'call %s() in %f %s'%(f.__name__, t, unit)
            return f(x)
        return fn1
    return fn

@performance('ms')
def factorial(n):
    return reduce(lambda x,y: x*y, range(1, n+1))
print factorial(10)

# 2-14 python中完善decorator
import time, functools

def performance(unit):
    def perf_decorator(f):
        @functools.wraps(f)
        def wrapper(*args, **kw):
            t1 = time.time()
            t2 = time.time()
            t = (t2 - t1)*1000 if unit =='ms' else (t2 - t1)
            print 'call %s() in %f %s'%(f.__name__, t, unit)
            return f(*args, **kw)
        return wrapper
    return perf_decorator
@performance('ms')
def factorial(n):
    return reduce(lambda x,y: x*y, range(1, n+1))
print factorial.__name__

# 2-15 python中偏函数
import functools
sorted_ignore_case = functools.partial(sorted, key = str.lower)
print sorted_ignore_case(['bob', 'about', 'Zoo', 'Credit'])

# 3-2 python之导入模块
from os.path import isdir,isfile
print isdir(r'/data/webroot/resource/python')
print isfile(r'/data/webroot/resource/python/test.txt')

# 3-3 pyhton中动态导入模块
try:
    import json
except ImportError:
    import simplejson as json
print json.dumps({'python':2.7})

# 3-4 pyhton之使用__future__
from __future__ import unicode_literals
s = 'am I an unicode?'
print isinstance(s, unicode)

# 4-2 pyhton之定义类并创建实例
class Person(object):
    pass
xiaoming = Person()
xiaohong = Person()
print xiaoming
print xiaohong
print xiaoming == xiaohong

# 4-3 python中创建实例属性
class Person(object):
    pass
p1 = Person()
p1.name = 'Bart'
p2 = Person()
p2.name = 'Adam'
p3 = Person()
p3.name = 'Lisa'
L1 = [p1, p2, p3]
L2 = sorted(L1, key = lambda x:x.name)
print L2[0].name
print L2[1].name
print L2[2].name

# 4-4 python中初始化实例属性
class Person(object):
    def __init__(self, name, sex, birth, job):
        self.name = name
        self.sex = sex
        self.birth = birth
        self.job = job

xiaoming = Person('Xiao Ming', 'Male', '1990-1-1', job='Student')

print xiaoming.name
print xiaoming.job

# 4-5 python中访问限制
class Person(object):
    def __init__(self, name, score):
        self.name = name
        self.__score = score

p = Person('Bob', 59)

print p.name
try :
    print p.__score
except AttributeError:
    print 'attributeerror'

# 4-6 python中创建类属性
class Person(object):
    count = 0
    def __init__(self, name):
        self.name = name
        Person.count += 1

p1 = Person('Bob')
print Person.count

p2 = Person('Alice')
print Person.count

p3 = Person('Tim')
print Person.count

# 4-7 python中类属性和实例属性名字冲突
class Person(object):

    __count = 0

    def __init__(self, name):
        self.name = name
        Person.__count +=1
        print Person.__count

p1 = Person('Bob')
p2 = Person('Alice')

try:
    print Person.__count
except AttributeError:
    print AttributeError

# 4-8 python中定义实例方法
class Person(object):

    def __init__(self, name, score):
        self.name = name
        self.__score = score

    def get_grade(self):
        if self.__score >= 90:
            return 'A'
        elif self.__score >= 60:
            return 'B'
        else:
            return 'C'

p1 = Person('Bob', 90)
p2 = Person('Alice', 65)
p3 = Person('Tim', 48)

print p1.get_grade()
print p2.get_grade()
print p3.get_grade()

# 4-9 python中方法也是属性
import types
def fn_get_grade(self):
    if self.score >= 80:
        return 'A'
    if self.score >= 60:
        return 'B'
    return 'C'

class Person(object):
    def __init__(self, name, score):
        self.name = name
        self.score = score

p1 = Person('Bob', 90)
p1.get_grade = types.MethodType(fn_get_grade, p1, Person)
print p1.get_grade()

#
class Person(object):
    def __init__(self, name, score):
        self.name = name
        self.score = score
        self.get_grade = lambda: 'A'
p1 = Person('Bob', 90)
print p1.get_grade
print p1.get_grade()

# 4-10 python中定义类方法
class Person(object):

    __count = 0
    @classmethod
    def how_many(cls):
        return cls.__count
    def __init__(self, name):
        self.nae = name
        Person.__count += 1

print Person.how_many()

p1 = Person('Bob')

print Person.how_many()

# 4-11 python中继承一个类
class Person(object):
    def __init__(self, name, gender):
        self.name = name
        self.gender = gender

class Teacher(Person):

    def __init__(self, name, gender, course):
        super(Teacher, self).__init__(name, gender)
        self.course = course

t = Teacher('Alice', 'Female', 'English')
print t.name
print t.course

# 5-3 python中判断类型
class Person(object):

    def __init__(self, name, gender):
        self.name = name
        self.gender = gender

class Student(Person):

    def __init__(self, name, gender, score):
        super(Student, self).__init__(name, gender)
        self.score = score

class Teacher(Person):

    def __init__(self, name, gender, course):
        super(Teacher, self).__init__(name, gender)
        self.course = course

t = Teacher('Alice', 'Female', 'English')

print isinstance(t, Person)
print isinstance(t, Student)
print isinstance(t, Teacher)
print isinstance(t, object)

# python中多态
import json

class Students(object):
    def read(self):
        return r'["Tim", "Bob", "Alice"]'

s = Students()
print json.load(s)

# 5-5 python中多重继承
class Person(object):
    pass

class Student(Person):
    pass

class Teacher(Person):
    pass

class SkillMixin(object):
    pass

class BasketballMixin(SkillMixin):
    def skill(self):
        return 'basketball'

class FootballMixin(SkillMixin):
    def skill(self):
        return 'football'

class BStudent(Student, BasketballMixin):
    pass

class FTeacher(Teacher, FootballMixin):
    pass

s = BStudent()
print s.skill()

t = FTeacher()
print t.skill()

# 5-6 python中获取对象信息
# kw传入一个dict,因此需要获取kye和values
#dir()返回的属性是字符串列表，如果已知一个属性名称，要获取或者设置对象的属性，就需要用 getattr() 和 setattr( )函数了
class Person(object):

    def __init__(self, name, gender, **kw):
        self.name = name
        self.gender = gender
        for k, v in kw.items():
            setattr(self, k, v)


p = Person('Bob', 'Male', age=18, course='Python')
print p.age
print p.course

# 6-2 python中__str__和__repr__
# __str__()用于显示给用户，而__repr__()用于显示给开发人员
class Person(object):

    def __init__(self, name, gender):
        self.name = name
        self.gender = gender


class Student(Person):
    def __init__(self, name, gender, score):
        super(Student, self).__init__(name, gender)
        self.score = score
    def __str__(self):
        return '(Student:%s, %s, %d)' % (self.name, self.gender, self.score)
    __repr__ = __str__

s = Student('Bob', 'male', 88)
print s

# 6-3 python中__cmp__
class Student(object):

    def __init__(self, name, score):
        self.name = name
        self.score = score

    def __str__(self):
        return '(%s: %s)' % (self.name, self.score)

    __repr__ = __str__

    def __cmp__(self, s):
        if self.score < s.score:
            return 1
        elif self.score > s.score:
            return -1
        else:
            if self.name < s.name:
                return -1
            else:
                return 1

L = [Student('Tim', 99), Student('Bob', 88), Student('Alice', 99)]
print
sorted(L)

# 6-4 pyhton中__len__
class Fib(object):

    def __init__(self, num):
        self.num = num
        self.fibo = [0, 1]
        i = 2
        while i < self.num:
            self.fibo.append(self.fibo[i - 2] + self.fibo[i - 1])
            i = i + 1

    def __str__(self):
        return str(self.fibo)

    def __len__(self):
        return len(self.fibo)


f = Fib(10)
print
f
print
len(f)

# 6-6 python中类型转换
class Rational(object):
    def __init__(self, p, q):
        self.p = p
        self.q = q

    def __int__(self):
        return self.p // self.q

    def __float__(self):
        return self.p / self.q

print float(Rational(7, 2))
print float(Rational(1, 3))

# 6-7 python中@property
class Student(object):

    def __init__(self, name, score):
        self.name = name
        self.__score = score

    @property
    def score(self):
        return self.__score

    @score.setter
    def score(self, score):
        if score < 0 or score > 100:
            raise ValueError('invalid score')
        self.__score = score

    @property
    def grade(self):
        if self.__score >= 80:
            return 'A'
        elif self.__score >= 60:
            return 'B'
        else:
            return 'C'

s = Student('Bob', 59)
print s.grade

s.score = 60
print s.grade

s.score = 99
print s.grade

# 6-8 python中__slots__
# __slots__的目的是限制当前类所能拥有的属性，如果不需要添加任意动态的属性，使用__slots__也能节省内存。
class Person(object):

    __slots__ = ('name', 'gender')

    def __init__(self, name, gender):
        self.name = name
        self.gender = gender

class Student(Person):

    __slots__ = ('name', 'gender', 'score')

    def __init__(self, name, gender, score):
        super(Student, self).__init__(name, gender)

s = Student('Bob', 'male', 59)
s.name = 'Tim'
s.score = 99
print s.score

# 6-9 python中__call__
class Fib(object):
    def __call__(self,num):
        L = [0,1]
        i = 2
        while i < num:
            L.append(L[i-2]+L[i-1])
            i=i+1
        return L

f = Fib()
print f(10)

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