找找你所需要的python小技巧

浅浅的花香味﹌ 2022-12-07 12:45 163阅读 0赞

# list洗牌(将list打乱) #

import random 
    alist = [1,2,3,4,5]
    random.shuffle(alist) 
    print(alist) #[4, 2, 1, 3, 5]

# 对字典的value进行排序 #

sorted(d.items(),key=lambda x:x[1])

# 字符串转字典 #

str1 ="k:1|k1:2|k2:3|k3:4" 
    def str2dict(str1): 
    	dict1 = { } 
    	for iterms in str1.split('|'): 
    		key,value =iterms.split(':') 
    		dict1[key] = value 
    	return dict1 
    #字典推导式 
    d = { k:int(v) for t in str1.split("|") for k, v in (t.split(":"), )}

# 寻找二个列表中的不同元素和相同元素 #

list1 = [1,2,3]
    list2 = [3,4,5]
    set1 = set(list1)
    set2 = set(list2)
    print(set1 & set2) #{3}
    print(set1 ^ set2) #{1, 2, 4, 5}

# 列表去重 #

l1 = ['b','c','d','c','a','a']
    l2 = list(set(l1))

# python如何实现单例模式 #

**方法一:装饰器**

def singleton(cls): 
    	instances = { } 
    	def wrapper(*args, **kwargs): 
    		if cls not in instances: 
    			instances[cls] = cls(*args,**kwargs)
    		return instances[cls] 
    	return wrapper
    @singleton 
    class Foo(object): 
    	pass 
    foo1 = Foo() 
    foo2 = Foo() 
    print(foo1 is foo2) # True

**方法二:使用基类**  
New 是真正创建实例对象的方法，所以重写基类的new 方法，以此保证创建对象的时候只生成一个实例

class Singleton(object): 
    	def new (cls, *args, **kwargs): 
    		if not hasattr(cls, '_instance'): 
    			cls._instance = super(Singleton, cls). new (cls, *args, **kwargs) 	
    		return cls._instance
    class Foo(Singleton):
     		pass
    foo1 = Foo() 
    foo2 = Foo() 
    print(foo1 is foo2) # True

**第三种:元类**  
元类是用于创建类对象的类，类对象创建实例对象时一定要调用call方法，因此在 调用call时候保证始终只创建一个实例即可，type是python的元类

class Singleton(type):
        def __call__(cls, *args, **kwargs):
            if not hasattr(cls,'_instance'):
                cls._instance = super(Singleton, cls).__call__ (*args, **kwargs)
            return cls._instance
    # Python3
    class Foo(metaclass=Singleton):
        pass
    foo1 = Foo()
    foo2 = Foo()
    print(foo1 is foo2) # True

**方法一:**

import os
    def get_files(dir,suffix):
        res = []
        for root,dirs,files in os.walk(dir):
            for filename in files:
                name,suf =os.path.splitext(filename)
                if suf == suffix:
                    res.append(os.path.join(root,filename))
        print(res)
    get_files("./",'.txt')

**方法二:**

import os
    def pick(obj):
        if obj.endswith(".txt"):
            print(obj)
    def scan_path(ph):
        file_list =os.listdir(ph)
        for obj in file_list:
            if os.path.isfile(obj):
                pick(obj)
            elif os.path.isdir(obj):
                scan_path(obj)
    if __name__ == '__main__':
        path = input('输入目录:')
        scan_path(path)

**第三种方法:**

from glob import iglob
    def func(fp, postfix):
        for i in iglob(f"{fp}/**/*{postfix}", recursive=True):
            print(i)
    if __name__ == '__main__':
        postfix = ".txt"
        func("目录名", postfix)

# 列表遍历时删除元素的正确操作 #

a = [1,2,3,4,5,6,7,8]
    for i in a[:]:
        if i%2==0:
            a.remove(i)
    print(a) #[1, 3, 5, 7]

# 字符串转数字(不用atoi函数) #

from functools import reduce 
    def atoi(s): 
        return reduce(lambda num, v: num * 10 + ord(v) - ord('0'), s,0)
    print(atoi("123")) #123a