Python的24个小技巧

柔情只为你懂 2022-04-06 04:08 309阅读 0赞

# python中相对不常见却很实用的小窍门 #

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### **空谈不如来码代码吧：** ###

--------------------

## **交换变量值** ##

"""pythonic way of value swapping"""
    a, b = 5, 10
    print(a, b)
    a, b = b, a
    print(a, b)

--------------------

## **给列表元素创建新的分隔符** ##

a = ["Python", "is", "awesome"]
    print(" ".join(a))

--------------------

## **找列表中出现次数最多的元素** ##

""" most frequent element in a list """
    a = [1, 2, 3, 1, 2, 3, 2, 2, 4, 5, 1]
    print(max(set(a), key=a.count))
    
    """ using Counter from collections """
    from collections import Counter
    cnt = Counter(a)
    print(cnt.most_common(3))

--------------------

## **核对两个字符是否为回文** ##

from collections import Counter
    str1 = "123456"
    str2 = "654321"
    if Counter(str1) == Counter(str2):
        print("回文")

--------------------

## **反向输出字符串** ##

""" 方法一 """
    a = "abcdefghijkmnopqrstuvwxyz"
    print(a[::-1])
    
    """ 方法二 """
    for char in reversed(a):
        print(char)
    
    """ 方法三 """
    num = 123456789
    print(int(str(num)[::-1]))

--------------------

## **反向输出列表** ##

""" 方法一 """
    a = [5, 4, 3, 2, 1]
    print(a[::-1])
    
    """ 方法二 """
    for i in reversed(a):
        print(i)

--------------------

## **转置2维数组** ##

original = [['a', 'b'], ['c', 'd'], ['e', 'f']]
    transposed = zip(*original)
    print(list(transposed))
    # [('a', 'c', 'e'), ('b', 'd', 'f')]

--------------------

## **链式比较** ##

s = 6
    print(3 < s < 8)
    print(2 == s < 10)
    # True
    # False

--------------------

## **函数的链式写法** ##

def product(a, b):
        return a * b
    
    
    def add(a, b):
        return a + b
    
    
    b = True
    print((product if b else add)(5, 7))
    # 35

--------------------

## **复制列表** ##

a = [1, 2, 3, 4, 5]
    b = a
    b[0] = 10
    print(b)
    # [10, 2, 3, 4, 5]
    
    b = a[:]
    b[0] = 10
    print(b)
    # [10, 2, 3, 4, 5]
    
    a = [1, 2, 3, 4, 5]
    print(list(a))
    # [1, 2, 3, 4, 5]
    
    print(a.copy())
    # [1, 2, 3, 4, 5]
    
    from copy import deepcopy
    l = [[1, 2], [3, 4]]
    l2 = deepcopy(l)
    print(l2)
    # [[1, 2], [3, 4]]

--------------------

## **字典的添加** ##

dicts = {'a': 1, 'b': 2}
    print(dicts.get('c', 3))
    # 3

--------------------

## **对字典的值排序** ##

d = {'a': 10, 'b': 20, 'c': 5, 'd': 1}
    print(sorted(d.items(), key=lambda x: x[1]))
    # [('d', 1), ('c', 5), ('a', 10), ('b', 20)]
    
    from operator import itemgetter
    print(sorted(d.items(), key=itemgetter(1)))
    # [('d', 1), ('c', 5), ('a', 10), ('b', 20)]

--------------------

## **for else结构** ##

a = [1, 2, 3, 4, 5]
    for i in a:
        if i == 0:
            break
    else:
        print("did not break out of for loop")

--------------------

## **将列表转换为逗号分隔** ##

l = ['foo', 'bar', 'xyz']
    print(','.join(l))
    # foo,bar,xyz
    
    num = [2, 3, 4, 5, 10]
    print(','.join(map(str, num)))
    # 2,3,4,5,10
    
    data = [2, 'hello', 3, 3.4]
    print(','.join(map(str, data)))
    # 2,hello,3,3.4

--------------------

## **字典的合并** ##

d1 = {'a': 1}
    d2 = {'b': 2}
    # pyhton 3.5
    print({**d1, **d2})
    # {'a': 1, 'b': 2}
    
    print(dict(d1.items() | d2.items()))
    # {'b': 2, 'a': 1}
    
    d1.update(d2)
    print(d1)
    # {'a': 1, 'b': 2}

--------------------

## **找列表中最大、最小值下标** ##

li = [20, 50, 80, 10, 55]
    
    
    def minIndex(li):
        return min(range(len(li)), key=li.__getitem__)
    
    
    def maxIndex(li):
        return max(range(len(li)), key=li.__getitem__)
    
    
    print(minIndex(li))
    # 3
    print(maxIndex(li))
    # 2

--------------------

## **从列表中删除重复项** ##

li = [2, 2, 3, 1, 3, 5, 6, 1]
    
    newli = list(set(li))
    print(newli)
    # [1, 2, 3, 5, 6]
    
    from collections import OrderedDict
    li = ["foo", "bar", "bar", "foo"]
    print(list(OrderedDict.fromkeys(li).keys()))
    # ['foo', 'bar']

--------------------

## **all or any** ##

x = [True, True, False]
    if any(x):
        print("至少有一个是True!")
    
    if all(x):
        print("没有一个是False！")
    
    if any(x) and not all(x):
        print("至少一个True和一个False！")
    
    # 至少有一个是True!
    # 至少一个True和一个False！

--------------------

## **emoji** ##

from emoji import emojize
    print(emojize(":thumbs_up"))

--------------------

## **\*\*kwargs** ##

dic = {'a': 1, 'b': 2}
    
    
    def someFunction(a, b):
        print(a + b)
        return
    
    
    someFunction(**dic)
    someFunction(a=1, b=2)

--------------------

## **三元运算** ##

a = 1
    b = 5
    
    if (a > b):
        print(a)
    else:
        print(b)
    
    
    print(a) if a > b else print(b)

--------------------

## **阶乘** ##

i = 1
    p = 1
    n = input("输入：")
    while i <= int(n):
        p = p * i
        i += 1
    print("结果：" + str(p))

--------------------

## **set(集合)数据结构** ##

# set(集合)是一个非常有用的数据结构。它与列表(list)的行为类似，区别在于set不能包含重复的值。
    # 这在很多情况下非常有用。例如你可能想检查列表中是否包含重复的元素，
    # 你有两个选择，第一个需要使用for循环，就像这样：
    some_list = ['a', 'b', 'c', 'b', 'd', 'm', 'n', 'n']
    
    duplicates = []
    for value in some_list:
        if some_list.count(value) > 1:
            if value not in duplicates:
                duplicates.append(value)
    
    print(duplicates)
    # 输出: ['b', 'n']
    
    
    # 但还有一种更简单更优雅的解决方案，那就是使用集合(sets)，你直接这样做：
    some_list = ['a', 'b', 'c', 'b', 'd', 'm', 'n', 'n']
    duplicates = set([x for x in some_list if some_list.count(x) > 1])
    print(duplicates)
    # 输出: set(['b', 'n'])
    
    
    # 集合还有一些其它方法，下面我们介绍其中一部分。
    
    # =========交集=========
    # 你可以对比两个集合的交集（两个集合中都有的数据），如下：
    valid = set(['yellow', 'red', 'blue', 'green', 'black'])
    input_set = set(['red', 'brown'])
    print(input_set.intersection(valid))
    # 输出: set(['red'])
    
    
    # =========差集===========
    # 你可以用差集(difference)找出无效的数据，相当于用一个集合减去另一个集合的数据，例如：
    valid = set(['yellow', 'red', 'blue', 'green', 'black'])
    input_set = set(['red', 'brown'])
    print(input_set.difference(valid))
    # 输出: set(['brown'])
    
    
    # 你也可以用符号来创建集合，如：
    a_set = {'red', 'blue', 'green'}
    print(type(a_set))
    # 输出: <type 'set'>

--------------------

## **ZIP** ##

keys = ['a', 'b', 'c']
    valus = [1, 2, 3]
    zippend = dict(zip(keys, valus))
    print(zippend)
    # {'a': 1, 'b': 2, 'c': 3}

--------------------

## ##

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