Functions, Parameters, and Globals
CS 233 Python Lecture Examples
#!/usr/bin/python
# References inside functions are local...
snoggle = 17
def wongle(n):
snoggle = n
print 'A:', snoggle,
wongle(235)
print snoggle
# ...unless declared global.
def wangle(n):
global snoggle
snoggle = n
print 'B:', snoggle,
wangle(235)
print snoggle
# Arguments are pass-by-value...
def snapple(n):
n = 55
print 'C:', snoggle,
wangle(snoggle)
print snoggle
# ...except for the contents objects, such as lists...
def snarffle(z):
z.append(22)
toggle = [ 'a', 'b', 'c' ];
print 'D:', toggle,
snarffle(toggle)
print toggle
# ...which means the contents of the object, not the parameter.
def snarggle(z):
z = [ 4, 5 ]
print 'F:', toggle,
snarggle(toggle)
print toggle
Argument passing in Python is a lot like Java.
Arguments are passed by value, so that changing a parameter
does not change the value at the caller.
However, objects (including built-in types
which are represented as objects) are passed as references, so using the
the paramater to change them will make changes visible to the caller.
