Python cannot see global variable

Question

Although i am specyfing a variable as global inside a function like this:

def SECdownload(year, month):
    import os
    from urllib.request import urlopen
    root = None
    feedFile = None
    feedData = None
    good_read = False
    itemIndex = 0
    edgarFilingsFeed = 'http://www.sec.gov/Archives/edgar/monthly/xbrlrss-' + str(year) + '-' + str(month).zfill(2) + '.xml'
    return edgarFilingsFeed
    #print( edgarFilingsFeed ) #from the slides
    if not os.path.exists( "sec/" + str(year) ):
        os.makedirs( "sec/" + str(year) )
    if not os.path.exists( "sec/" + str(year) + '/' + str(month).zfill(2) ):
        os.makedirs( "sec/" + str(year) + '/' + str(month).zfill(2) )
    global target_dir
    target_dir = "sec/" + str(year) + '/' + str(month).zfill(2) + '/'

And then i import the function and then run it in the Python UI (Windows) like this:

>>> from df import SECdownload
>>> SECdownload(2012,4)

Why when i type the variable target_dir in the Shell i get:

>>> target_dir
Traceback (most recent call last):
File "<pyshell#6>", line 1, in <module>
    target_dir

NameError: name 'target_dir' is not defined

How is this possible when i clearly state inside the function that the variable is global ?

Answer 1

由于以下这一行，您无法处理全局变量的代码：

return edgarFilingsFeed

Answer 2

Functions work in the context in which they were created. That is, any globals they work with are local to the module that the function was created in.

For instance:

m.py:

def a(val):
    global x
    x = val

main.py

from m import a
a(10)
import m
print(m.x)

produces 10