Assume that I have this code (at Python):
a=1
b=2
c=3
def x(a,b,c):
a=5
b=6
c=7
x(a,b,c)
print(a,b,c)
The output will be: 1 2 3
My question is:
There is a why to change the values of a,b,c at x(a,b,c) (without return)?
Thank you!
Using the global keyword:
a=1
b=2
c=3
def x():
global a, b, c
a = 5
b = 6
c = 7
x()
print(a,b,c)
# -> 5 6 7
Using a class:
class Foo(object):
def __init__(self, a, b, c):
self.a = a
self.b = b
self.c = c
def x(self):
self.a = 5
self.b = 6
self.c = 7
foo = Foo(1, 2, 3)
print(foo.a, foo.b, foo.c)
# -> 1 2 3
foo.x()
print(foo.a, foo.b, foo.c)
# -> 5 6 7
global works, but as a new Python Programmer you should try to avoid it as a default pattern.A workaround would be to convert it into a list, as follows:
a = 1
b = 2
c = 3
l = [a, b, c]
def x(list):
list[:] = [5, 6, 7]
x(l)
a, b, c = l
print(a, b, c)
As a new Python Programmer, PLEASE AVOID the use of global. Globals may be useful for things like configuration, but for the most part they can cause dangerous side effects if you start to use them as your default programming paradigm. I'd suggest you try a class pattern, or variable assignment pattern.
Class Assignment
class Foo(object):
def __init__(self, a, b, c):
self.a = a
self.b = b
self.c = c
def update(self, a, b, c):
self.a = a
self.b = b
self.c = c
foo = Foo(1,2,3)
foo.update(5,6,7)
print "a: %d, b: %d, c: %d" % (foo.a, foo.b, foo.c)
Variable Assignment
a=1
b=2
c=3
def x():
a_prime = 5
b_prime = 6
c_prime = 7
return a_prime, b_prime, c_prime
a, b, c = x()
print a, b, c
So you can use the global modifier inside of the function to make the variables refer to the ones outside the function; however, this can result in a "code smell".
So inside the function, place global before those assignments and that should fix your problem.
x(and not pass them as parameters). There's no way to do this via parameters, as a parameter conveys only a value - there's absolutely no connection to the variable the value came from.