Assigning global variable to a local variable

Asked Jan 05 '17 at 18:07

Active Jan 05 '17 at 18:10

Viewed 39 times

When I assign a Global list to a local list and edit this local list both the list get edited. Is it because list in python are pointer, similar to array in C?

>>> source = [(0, 5), (1, 5), (2, 5), (3, 5), (4, 5)]
>>> def s():
...     source_queue = source
...     while len(source_queue)>0:
...             f(source_queue)
...
>>> def f(source_queue):
...     (x,y) = source_queue.pop(0)
...     print (x,y) in source
...     print source,source_queue
...
>>> s()

Output:

False
[(1, 5), (2, 5), (3, 5), (4, 5)] [(1, 5), (2, 5), (3, 5), (4, 5)]
False
[(2, 5), (3, 5), (4, 5)] [(2, 5), (3, 5), (4, 5)]
False
[(3, 5), (4, 5)] [(3, 5), (4, 5)]
False
[(4, 5)] [(4, 5)]
False
[] []

edited Jan 05 '17 at 18:10

asked Jan 05 '17 at 18:07

Abuhujair Khan

Do you have any question? – Axnyff Jan 05 '17 at 18:09
"similar to array in C?" - no. See http://nedbatchelder.com/text/names.html. – user2357112 Jan 05 '17 at 18:10
they share the same reference, that's why. – Jean-François Fabre Jan 05 '17 at 18:10
Yes. How can I prevent the Global list by getting edited? – Abuhujair Khan Jan 05 '17 at 18:11
Damn! dupehammer is working at its full (and it's for the best!) – Jean-François Fabre Jan 05 '17 at 18:11
If you want to prevent the global list form being edited you can copy it : `new_list = old_list[:]` – Samuel Yvon Jan 05 '17 at 18:12
Try `source_queue = list(source)` – moogle Jan 05 '17 at 18:12

Assigning global variable to a local variable

0 Answers0