Python赋值语句中的逻辑变量

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本文链接： https://blog.csdn.net/JosephThatwho/article/details/101309214

在Python赋值时可以使用or代替if…else…达到简化代码的作用

def assign_with_or(a=None, b=None):
    res = a or b
    print (res)
    
    
if __name__ == '__main__':
    assign_with_or(a='a') 
    assign_with_or(a='a', b='b')
    assign_with_or(b='b')

其中assign_with_or()等价于如下函数

def assign_with_or(a=None, b=None):
    if a:
        res = a
    else:
        res = b
    print (res)
    
    
if __name__ == '__main__':
    assign_with_or(a='a')
    assign_with_or(a='a', b='b')
    assign_with_or(b='b')

两个函数输出结果一致

root@root:~/Desktop$ python3 test.py
a
a
b

进一步，and也可以用在赋值语句中

def assign_with_log_opr(a=None, b=None, c=None):
    res = a and b or c
    print (res)
     
     
if __name__ == '__main__':
    assign_with_log_opr(a='a', b='b', c='c')
    assign_with_log_opr(b='b', c='c')
    assign_with_log_opr(a='a', c='c')
    assign_with_log_opr(a='a')

上述‘assign_with log_opr()’输出结果为

b
c
c
None

等价于

def func(a=None, b=None, c=None):
    if a and b:
        res = b
   else:
        res = c
   print (res)

在Django中也用到这种语法，Django初始化项目时调用的模块’Django/core/management/__init__.py’:

class ManagementUtility:
    """
    Encapsulate the logic of the django-admin and manage.py utilities.
    """
    def __init__(self, argv=None):  
        self.argv = argv or sys.argv[:] 
        self.prog_name = os.path.basename(self.argv[0])
       ...