Python入门二：函数

            1
            def
             函数名(参数):

            2
            """
            3
                文档字符串

            4
            """
            5
                函数体

            6
                返回值

            7
        

            1
            def
             func(argument):

            2
            print
            (argument)

            3
            

            4
            5 func("string")
6 func(4)

            1
            def func(name, age = 20):
2print(name, age)
345 func("Edward")
6 func("Edward", 18)

             1
            def func(*args, **kwargs):
 2for i in args:
 3print(i)
 4for k, v in kwargs.items():
 5print("%s = %s" % (k, v))
 6 7 8 func("Edward", 19)
 9 func(name = "Edward", age = 19)
10 func("Edward", "Tang", age = 19)    

            1 tup = ("Edward", 19)
2 dic = dict(name = "Edward", age = 19)
3 func(*tup)
4 func(**dic)
5# 如果不加*， 会被认为是tuple的一个元素

            1
            def
             func(a):

            2
            return a * a, a ** a
345 x, y = func(4) # x = 16, y = 256

            1
            def
             func()

            2
            pass
            3
            4
            5
            if
            __name__ == "__main__":
6     func()

            1 a = lambda x: x ** 2
2 a(2)
3# 4

             1 seq = [1, 76, 5, 44, 13,  5, 23]
 2 3 a = filter(lambda x : x > 10, seq)
 4# list(a) = [76, 44, 13, 23] 5 6 b = map(lambda x : x ** 2, seq)
 7# list(b) = [1, 5776, 25, 1936, 169, 25, 529] 8 9from functools import reduce
10 c = reduce(lambda x, y: x * y, range(1, 100))
11# c的结果为99！

            1 seq = ["Tang", "Edward", "love", "handsome"]
2 seq = sorted(seq, key=lambda a : a.upper())
3# seq = [‘Edward‘, ‘handsome‘, ‘love‘, ‘Tang‘]

             1
            class
             Student(object):

             2
            def
            __init__
            (self, name):

             3         self.name = name
 4 5def have_class(self):
 6print("%s is having class." % self.name)
 7 8 s = Student("Edward")
 910# name 以下都必须是字符串格式1112# hasattr(object, name), 判断对象是否具有name属性13print(hasattr(s, "name"))    # True14print(hasattr(s, "have_class"))    # True1516# getattr(object, name, default=None), 返回对象的name属性的值17# 可以设置default, 但是仅仅是没有找到时返回它，并没有添加18print(getattr(s, "name"))    # Edward19print(getattr(s, "age", 19))  # 1920 getattr(s, "have_class")()    # 会运行该属性21print(hasattr(s, "age"))    # False, 并没有添加2223# setattr(object, name, value), 设置对象的name的属性值为value24# 若name属性不存在， 还会添加该属性25 setattr(s, "name", "Tang")
26print(s.name)   # Tang27 setattr(s, "age", 19)
28print(hasattr(s, "age"))  # True, 会添加该属性2930# delattr(object, name) 删除对象的name属性31 delattr(s, "name")
32print(hasattr(s, "name"))  # False, 已被删除

            1
            #
             exec(), 动态执行代码
            2
            exec("print(‘Edward Tang‘)")
34# eval() 计算表达式的值并放回5 a = eval("7 * 6 + 1")
6print(a) # 43

             1
            def
             func1(n):

             2
            if n > 10:
 3return True
 4 5def func2(n):
 6return n * n
 7 8def func3(a, b, c):
 9return a * b * c
101112 seq = [1, 76, 5, 44, 13, 3, 5, 23]
13 li1 = [4, 5, 6, 8]
14 li2 = [9, 7, 10, 6]
15 li3 = [5, 4, 3, 1]
161718# filter对seq中的每一个元素执行func1, 如果为True, 返回原列表的这些值19 rt1 = filter(func1, seq)
20print(list(rt1))
2122# map对seq中的每一个元素执行func2，返回这些值执行的结果构成的序列23 rt2 = map(func2, seq)
24print(list(rt2))
2526# 若func有多个参数，可以提供多个序列，分别依次带入，返回结果27 rt3 = map(func3, li1, li2, li3)
28print(list(rt3))
2930# 在functools中还存在一个reduce的函数31# reduce(func, seq, start) func接受两个参数，32# 对seq中两两的数进行递归调用，并返回33from functools import reduce
34def  func(a, b):
35return a * b
36 rt = reduce(func, range(1, 100))
37# 计算99的阶乘

             1
            #
             sorted(iterable, key=None, reverse=False)
             2
            #
             key可以用函数或lambda表达式
             3
            #
             指定reverse = True会降序排序
             4
            #
             sorted只是返回一个排序好的序列，并不改变原序列
             5
             6
            #
             普通排序
             7 seq = [1, 76, 5, 44, 13, 3, 5, 23]
 8 seq = sorted(seq, reverse=True) # 降序 910#使用lambda11 seq = ["Tang", "Edward", "love", "handsome"]
12 seq = sorted(seq, key=lambda a : a.upper())
1314# 对列表的某项排序15 arr = [[‘Tang‘, 89], [‘Edward‘, 79], [‘Hu‘, 67], [‘Wang‘, 80]]
16 arr = sorted(arr, key=lambda a : a[1])
1718# 对类按照某项排序19class Person(object):
20def__init__(self, name, age):
21         self.name = name
22         self.age = age
23 p1 = Person(‘Edward‘, 18)
24 p2 = Person(‘Wang‘, 25)
25 p3 = Person(‘Hu‘, 20)
26 p4 = Person(‘Liang‘, 22)
27for item in sorted([p1, p2, p3, p4], key=lambda p : p.age):
28print(item.name, end=‘,‘)
2930# operator模块还有itemgetter, attrgetter两个函数31# 所以以上最后两个例子还可以表示为32# sorted(arr, key=itemgetter(1))33# sorted([p1, p2, p3, p4], key=attrgetter(‘age‘))

             1
            #
             enumerate(iterable, start=0)
             2
            #
             用于循环中，同时得到iterable的值和计数
             3 lst = [‘Edward‘, ‘Tang‘, ‘Wang‘, ‘Hu‘]
 4for index, item in enumerate(lst):
 5print(index, item)
 6 7# zip(iter1 [,iter2 [...]]) 8# 分别从iter中取下标相同的元素构成tuple，再将各tuple构成list 9# 使用zip(*list) 做相反的操作10 x = [1, 2, 3]
11 y = [4, 5, 6]
12 z = [7, 8, 9]
13 w = zip(x, y, z)
14print(list(w))  # [(1, 4, 7), (2, 5, 8), (3, 6, 9)]15# 用在循环中16for a, b, c in zip(x, y, z):
17print(a, b, c) 

            1 a = iter([3, 6, 1, 9])
2 a.__next__()   # 33 a.__next__()   # 6

            1
            from collections import Iterable
2 lst = [1, 5, 6, 9]
3 isinstance(lst, Iterable)   # True

            1 a = (x * x for x in range(1, 10))
2print(a.__next__())    # 1    3print(a.__next__())    # 4

             1
            def
             func(n):

             2     a = 1
 3while a < n:
 4yield a 
 5         a += 2
 6 7 f = func(10)
 8print(f.__next__())    # 1  9print(f.__next__()) # 31011# 通过yield还可以模拟实现多线程

             1
            def
             func(n):

             2     a = 1
 3while a < n:
 4         b = (yield a)
 5if b == None:
 6             b = 0
 7         a += b
 8 9 f = func(10)
10print(f.__next__())    # 111print(f.__next__())    # 112print(f.send(5))          # 613print(f.__next__())    # 6

             1
            def
             deco(func):

             2
            def
             inner():

             3
            print("Edward")
 5print("tang")
 6return func()
 7return inner
 8 910@deco
11def func():
12print("handsome")
13 
14 # 并不一定需要以返回func()的方式执行func(这种情况函数需要最后执行),可以先将其返回值保存在一个变量中，最后将其返回
15
16 def inner():
17 　　print("Edward")
18　　 rt = func()
19 　　print("tang")
20    return rt
21 
22# 相当于重新定制了func

             1
            def
             deco(func):

             2
            def
             inner(str1):

             3
            print("Edward")
 4return func(str1)
 5return inner
 6 7@deco
 8def func(str1):
 9print(str1)
1011 func("Tang")
1213# 保持inner()函数的参数和原来的func()一样多即可 

             1
            def
             de1(func):

             2
            def
             inner():

             3
            print("Edward")
 4return func()
 5return inner
 6 7def de2(func):
 8def inner():
 9print(‘tang‘)
10return func()
11return inner
121314@de1
15@de2
16def func():
17print("handsome")
1819func()
2021# 相当于func = de1(de2(func()))

             1
            def
             deco(func):

             2
            #
             @functools.wraps(func)
             3
            def
             inner():

             4
            print("Edward")
 5print("tang")
 6return func()
 7return inner
 8 9@deco
10def func():
11""" A hansome boy! """12print("handsome")
1314print(func.__name__)
15print(func.__doc__)
1617# 会输出 inner和None18# 如果去掉注释,  输出func和A handsome boy! 

            1
            from operator import add, mul
2from functools import partial
34 add1 = partial(add, 1)
5 mul100 = partial(mul, 100)
67print(add1(99))  # 1008print(mul100(99))  # 9900

             1
            """
            easy_gui.py
            """
             2
             3
            from functools import partial
 4import tkinter
 5# Tkinter模块是python中一个能快速创建GUI的标准库 6 7 root = tkinter.Tk()
 8# 创建一个顶层窗口对象 9 MyButton = partial(tkinter.Button, root, fg=‘white‘, bg=‘blue‘)
10# 用偏函数设置按钮的默认属性11 b1 = MyButton(text=‘Button 1‘)
12 b2 = MyButton(text=‘Button 2‘)
13 qb = MyButton(text=‘QUIT‘, bg=‘red‘, command=root.quit)
14b1.pack()
15b2.pack()
16 qb.pack(fill=tkinter.X, expand=True)
17 root.title(‘PFAs!‘)
18 root.mainloop()

             1
            """
            模拟100以内的加减乘除运算
            """
             2
             3
            from operator import add, sub, mul, truediv
 4# operator模块提供了各种对python内置方法的访问 5from random import randint, choice
 6# random模块提供了各种随机数的生成 7# random() 生成一个[0, 1)之间的随机数 8# randrange(start, stop=None, step=1) 生成一个range(args)范围内的随机数 9# randint(a, b) 生成一个[a, b] 范围内的整数10# choice(seq) 从序列seq中随机获取一个元素11# shuffle(x) 洗牌序列x，返回None12# sample(population, k) 从population中随机获取k个元素并作为新的序列返回，但是原序列不变13# uniform(a, b) 返回一个a, b之间的浮点数141516 ops = {‘+‘: add, ‘-‘: sub, ‘*‘: mul, ‘/‘: truediv}
17 MAXTRIES = 2
18# 能够尝试的最大次数192021def doprob():
22""" get easy random equation and check the correctness of the input """23     op = choice(‘+-*/‘)
24# 随机获取运算符25     nums = [randint(1, 100) for i in range(2)]
26# 随机获取参与运算的两个数27     nums.sort(reverse=True)
28# 降序使结果不为负数29while op == ‘/‘:
30if nums[0] % nums[1] == 0 and nums[1] != 1:
31break32         nums = [randint(1, 100) for i in range(2)]
333435     ans = ops[op](*nums)
36     pr = ‘%d %s %d = ‘ % (nums[0], op, nums[1])
37     oops = 0
38# 尝试的次数39while True:
40try:
41if int(input(pr)) == ans:
42print(‘correct‘)
43break44if oops == MAXTRIES:
45print(‘answer\n%s%d‘ % (pr, ans))
46else:
47print(‘incorrect... try again‘)
48                 oops += 1
49except (KeyboardInterrupt,
50                EOFError, ValueError):
51print(‘invalid input... try again‘)
525354def main():
55""" realize the repetitive operation"""56while True:
57        doprob()
58try:
59             opt = input(‘Again? [y]‘).lower()
60if opt and opt[0] == ‘n‘:
61break62except (KeyboardInterrupt, EOFError):
63break646566if__name__ == ‘__main__‘:
67     main()

             1
            """
            闭包和装饰器的应用
            """
             2
             3
            from time import time
 4 5def logged(when):
 6def log(f, *args, **kwargs):
 7print(‘‘‘Called:
 8    function: %s
 9    args: %r
10    kargs: %r‘‘‘ % (f, args, kwargs))
11# %r repr   %s str1213def pre_logged(f):
14def wrapper(*args, **kwargs):
15             log(f, *args, **kwargs)
16return f(*args, **kwargs)
17return wrapper
1819def post_logged(f):
20def wrapped(*args, **kwargs):
21             now = time()
22try:
23return f(*args, **kwargs)
24finally:
25                 log(f, *args, **kwargs)
26print(‘time delta: %s‘ % (time()-now))
27return wrapped
2829try:
30return({‘pre‘: pre_logged, ‘post‘: post_logged}[when])
31except KeyError as e:
32raise(ValueError(e), ‘must be "pre" or "post"‘)
3334 @logged(‘post‘)
35def hello(name):
36print(‘hello,‘, name)
3738 hello(‘world!‘)