Then it’s easy to test whether a variable is bound toNone: if x is None: some_fallback_operation( ) else: some_operation(x) Discussion Python doesn’t have a specific function to test whether a variable is defined, since all variables are expected to have been defined before use, even...
We can use the in operator to check if the string of the variable name exists in the dictionary. If so, it means the variable exists in the local namespace; otherwise, not. The complete example code is as follows: def local_func(): var = "Test" if "var" in locals(): print("...
我们在上面代码的if分支中定义了一个变量a,这是一个全局变量(global variable),属于全局作用域,因为它没有定义在任何一个函数中。在上面的foo函数中我们定义了变量b,这是一个定义在函数中的局部变量(local variable),属于局部作用域,在foo函数的外部并不能访问到它;但对于foo函数内部的bar函数来说,变量b属于嵌套...
6 解决“name 'reload' is not defined和AttributeError: module 'sys' has no att”错误提示 在Python 3.6程序中不能直接使用reload,要想兼容Python 2中的reload功能,需要加入如下所示的代码: 1importimportlib 2importlib.reload(sys) 7 解决“python unico...
So if you have a variable, for example: one = 1 You want to know its type? There are right ways and wrong ways to do just about everything in Python. Here's the right way: Use type >>> type(one) <type 'int'> You can use the __name__ attribute to get the name of the...
I'm trying to test if one of my variables is pd.NaT. I know it is NaT, and still it won't pass the test. As an example, the following code prints nothing : a=pd.NaTifa == pd.NaT:print("a not NaT") Does anyone have a clue ? Is there a way to effectively test ifais NaT...
8 TestVariableScope.a=12 9 10 if __name__=='Demo': 11 print('Demo is running') 12 13 if __name__ == '__main__': 14 SetVariable() 15 TestVariableScope() 16 b=TestVariableScope 17 b() 1. 2. 3. 4. 5. 6. 7.
if ord(e) > 128: print("^ ", end='') else: print(' ', end='') print() s = "【a, b,中" find_chinese_char(s) s = "([10, 2,3,4】“])" find_chinese_char(s) 如果经常受困于这些错误,建议阅读代码里面的中、英文符号 - 知乎 (zhihu.com)。
module A : __main__ 1. 执行B.py 的结果: module A : test module B : __main__ 1. 2. 你们看出问题的所在了吧!模块 A 前后竟然出现了两个不同的名字。这两个名字是什么意思,又为什么会有这样的不同呢? 我想这正体现的是名字的本质吧——对自己来说,我就是我,并不需要一个名字来标记;而对他...
>>> a = 'test' >>> print(a) # 这里多了缩进 File "<stdin>", line 1 print(a) ^ IndentationError: unexpected indent >>> if a == 'tt': ... print(a) # 这里少了缩进,‘:’后应该有一个缩进。 File "<stdin>", line 2