I am new to python, and I am using a global variable to control my design easily, especially for debugging.
Here is my code:
hidNow = -1
def loginFromSql(br, n=0):
global hidNow
print hidNow
hidNow = 5566
print hidNow
print(hidNow)
And I run python directly with "from myModule import *"
Before calling the function, print hidNow get the result of -1, but it still -1 even the function is called....
Is it a bug in python? I am using python 2.7.5
Thanks!
If you do from myModule import *, you create a variable called hidNow in the place where you do the import. This new variable is separate from the hidNow inside myModule. They have the same value initially, but assigning a new value to hidNow from inside myModule will not change the value you already imported.
One solution is don't use the * import. Instead do:
import myModule
print myModule.hidNow
myModule.loginFromSql()
print myModule.hidNow # will change
(This is what I think you're asking, but your question and code are unclear, so please edit and correct it if this isn't what you're getting at.)
You should think about why you'e using a global variable to store this information. Global variables are fragile.
I am using a global variable to control my design easily, especially for debugging.
I'm going to gloss over the actual issue (as another answer has already pointed out the cause) and address the X part of this XY problem.
This is not really controlling your design easily like you may think, the use of global variables at the module level is usually not necessary and will appear to many python devs as a code smell.
A better way to maintain state is to use a class, which would go something like this:
# myModule.py
class Thing(object):
def __init__(self, hidNow=-1):
self.hidNow = hidNow
def loginFromSql(self, br, n=0):
self.hidNow = 5566
And here you see the access method for this attribute, and see the value change take place.
>>> from myModule import *
>>> my_thing = Thing()
>>> my_thing.hidNow
-1
>>> my_thing.loginFromSql('potato')
>>> my_thing.hidNow
5566
You defined loginFromSql but you did not call it. Here is your example script with a bit extra printing and a call to the function.
hidNow = -1
def loginFromSql(br, n=0):
global hidNow
print "login start", hidNow
hidNow = 5566
print "login done", hidNow
print "before call", hidNow
loginFromSql('x')
print "after call", hidNow
When you run it, you get this output, showing that the global does change
before call -1
login start -1
login done 5566
after call 5566
