Python的eval()和globals() [英] Python's eval() and globals()

问题描述

我正在尝试使用eval()执行许多功能，并且需要创建某种环境以使其运行.在文档中说，您可以将全局变量作为第二个参数传递给eval().

I'm trying to execute a number of functions using eval(), and I need to create some kind of environment for them to run. It is said in documentation that you can pass globals as a second parameter to eval().

但是对于我来说似乎不起作用.这是一个简化的示例(我尝试了两种方法，声明变量global和使用globals()，但两种方法都不起作用):

But it seems to not work in my case. Here's the simpified example (I tried two approaches, declaring variable global and using globals(), and both do not work):

import test

global test_variable
test_variable = 'test_value'
g = globals()
g['test_variable'] = 'test_value'
eval('test.my_func()', g)

文件 test.py :

def my_func():
    global test_variable
    print repr(test_variable)

我得到了:

NameError:未定义全局名称"test_variable".

NameError: global name 'test_variable' is not defined.

我应该怎么做才能将test_variable传递给my_func()?假设我不能将其作为参数传递.

What should I do to pass that test_variable into my_func()? Assuming I can't pass it as a parameter.

推荐答案

test_variable 在test.py中应该是全局的.之所以出现名称错误，是因为您试图声明一个尚不存在的全局变量.

test_variable should be global in test.py. You're getting a name error because you're trying to declare a variable global that doesn't yet exist.

因此，您的my_test.py文件应如下所示:

So your my_test.py file should be like this:

test_variable = None

def my_func():
    print test_variable

并在命令提示符下运行它:

And running this from the command prompt:

>>> import my_test
>>> eval('my_test.my_func()')
None
>>> my_test.test_variable = 'hello'
>>> my_test.test_variable
'hello'
>>> eval('my_test.my_func()')
hello

通常，使用eval()和全局变量是一种不好的形式，因此请确保您知道自己在做什么.

Generally it's bad form to use eval() and globals, so make sure you know what your doing.

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