Python语言中的常用技巧

た入场券 2022-05-16 01:11 174阅读 0赞

## 技巧罗列一下，以备后续常用 ##

1.包装与解包

a = (1,2,3)
    x,y,z = a

2.判断元素是否存在

## check whether it exists.
    bb = ['a', 'b', 'c']
    if 'a' in bb:
        print("let it be...")
    
    cc ={
       'a': 'a', 'b':'b', 'c':'c'}
    print('c' in cc)
    
    "s" in "stirng"
    
    "string".startswith('s')
    "string".endswith('g')

3.数组元素的切割

## 数组切割
    l2 = [1,2,3,4,5]
    l2[:4]
    l2[-2:]
    l2[3:]
    
    ## 1， 3， 5
    l2[::2]
    l2[-1]

4.三元表达式

# 三元表达式
    a if b else c

5.数组操作的快捷方式

m = list(), dict(), 
    
    m = (1,2,3,4)
    n = [i*2 for i in m]
    
    d = [x for i in m if i% 2 == 2]
    
    e = {x:x%2 == 0 for x in m}
    
    m = [1,2,3,4,5]
    i = (x for x in m)

6.lambda操作

## lambda synthex
    test =lambda x: (x+2)
    
    def test(x):
        x+2
    
    print(test(3)

7.数组集合操作

[1,2] + [3,4] ==> [1,2,3,4]
    
    [1,2].extend([3,4])  old array
    
    [1,2] * 2 ==> [1,2,1,2]
    
    "xx" * 2 ==> "xxxx"
    
    team = ['ab', 'cd', 'ef']
    
    for index, ele in enumerate(team):
        print(str(index) + ":" +ele)

8.常用的集合函数

# filter
    nums = [1,2,3,4]
    
    ##generator
    ## filter: filte
    ## map: do action for every element
    ## 
    l = filter(lambda x: x%2==0, nums)
    for i in l:
        print(i)
    
    ## zip
    nums1 = [1,2,3,4]
    nums2 = [5,6,7,8]
    
    l = zip(nums1, nums2)
    for i in l:
        print(i)
    
    ## reduce
    from functools import reduce
    teams = [1,2,3,4]
    l = reduce(lambda x,y: x+y, teams)
    for i in l:
        print(i)

这类是基于规则的操作函数， 可以基于lambda的快捷函数来实现，也可以自行定义。这类函数操作的结果都是generator，需要遍历之后方可访问。