Python 强化训练：第五篇

强化训练：第五篇

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主题：函数

1. 基本定义方法
2. 任意数量参数
3. 只接受关键字参数
4. 显示数据类型
5. 默认参数
6. 匿名函数
7. N个参数的可调用对象

0. 基本定义

def hanshu(*args):
    return sum(args)

print(hanshu(1, 2, 3, 4))    # 10

1. 任意数量参数

def avg(first, *args):
    return (first + sum(args))/(1 + len(args))

print(avg(3, 2, 3, 1))    # 2.25
print(avg(3, 4))    # 3.5

2. 关键字参数

def keywords(number, *, newnumber):
    return (number + newnumber)

print(keywords(3, newnumber=5))    # 8
#print(keywords(3, 2))   # wrong

3. 数据类型

def type_number(a:int, b:int)->int:
    return (a+b)

print(type_number(3, 4))    # 7
print(help(type_number))    
#Help on function type_number in module __main__:

#type_number(a:int, b:int) -> int

#None

4. 返回多个值

def larger_number(*args, **kwargs):

    return args, kwargs

print(larger_number(1, 2, 3, 4, a=1, b=2, c=3))
# ((1, 2, 3, 4), {'c': 3, 'b': 2, 'a': 1})

5. 默认参数

def define_key(*args, b=1156143589):
    return args, b

print(define_key(1, 2, 3, 4))
print(define_key(1, 2, 3, 4, 5, b=12))
#((1, 2, 3, 4), 1156143589)
#((1, 2, 3, 4, 5), 12)

6. 匿名函数/ 匿名函数绑定值

lam= lambda x, y: x + y

print(lam(2, 3))    # 5

lam_2= lambda x, y=2: x**y

print(lam_2(3))    # 9

lam_3 = lambda x=3, y=3: x==y

print(lam_3())    # True
print(lam_3(2))    # False
print(lam_3(2, 2))    # True

7. 减少可调用对象的参数个数

def define_seven(a, b, c, d):

    return (a, b, c, d)

print(define_seven(1, 2, 3, 4))
# (1, 2, 3, 4)

from functools import partial
seven = partial(define_seven, d=4)
print(seven(1, 2, 3)) # (1, 2, 3, 4)
seven_1 = partial(define_seven, 1)
print(seven_1(1, 2, 3))  #(1, 1, 2, 3)
seven_2 = partial(define_seven, 1, 2)
print(seven_2(1, 2))    #(1, 2, 1, 2)

from datetime import datetime, timedelta


def GetNextDay(baseday,n):
    return str((datetime.strptime(str(baseday),'%Y-%m-%d')+timedelta(days=n)).date())
for i in range(1, 8):
    NextDay = partial(GetNextDay, '2016-11-04')
    print(NextDay(i))
    
# 2016-11-05
# 2016-11-06
# 2016-11-07
# 2016-11-08
# 2016-11-09
# 2016-11-10
# 2016-11-11