如何在python中检查变量是否为空？


How to check if a variable is empty in python?

我想知道python是否有任何函数，比如php空函数(http://php.net/manual/en/function.empty.php)，用以下条件检查变量是否为空

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"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
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see also this which recommends the previous答案not关键字P＞＜／

how to check if a list is empty Python？P＞＜／

它只是generalizes to超过列表：P＞＜／

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>>> a =""
>>> not a
True

>>> a = []
>>> not a
True

>>> a = 0
>>> not a
True

>>> a = 0.0
>>> not a
True

>>> a = numpy.array([])
>>> not a
True

notably will not work for恩，因为"0"as a字符串字符串does the事实contain something -含字符"0"。for你have to convert it to an int：P＞＜／

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>>> a ="0"
>>> not a
False

>>> a = '0'
>>> not int(a)
True
相关讨论

是的，bool。这是not the same -确切的说因为是True'0'is，but NoneFalse[]0，，，，0.0和""False，是的。P＞＜／

当你implicitly boolis used condition评价对象在安安whilestatement类ifor expression，条件，或与布尔算子。P＞＜／

如果你想知道PHP字符串处理含as something like does，你可以给你：P＞＜／

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def empty(value):
    try:
        value = float(value)
    except ValueError:
        pass
    return bool(value)

see section 5.1：P＞＜／

docs.python.org http：/ / /图书馆/ stdtypes.htmlP＞＜／

任何对象的真值测试can be for if，for或while使用安布尔condition or as below of the操作操作数。下面的值是错误的事情考虑：P＞＜／

NoneP＞＜／

FalseP＞＜／

零for example of any type的值，00L0.0，，，，0j。P＞＜／

任何空序列，for example，''，()，[]。P＞＜／

任何for example，{}空映射。P＞＜／

用户定义的类的情况下)，或在__nonzero__()if the class defines __len__()method that when the method，返回布尔值False整数或零。[ 1 ]P＞＜／

在其他的事情考虑的对象的值是true of many types -我知道你是真实的。P＞＜／

操作和建立在布尔函数总是返回result that have a 0or for False虚假和1Truefor True or otherwise，除非stated。(例外：the important or总是返回布尔操作和操作数andone of their。)P＞＜／

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用途：只notP＞＜／

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if not your_variable:
    print("your_variable is empty")

用途：为你的0 as string布尔P＞＜／

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if your_variable =="0":
    print("your_variable is 0 (string)")

组合它们：P＞＜／

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if not your_variable or your_variable =="0":
    print("your_variable is empty")

Python简单is this is about)，我知道答案：P＞＜／