There is no pass by reference in Python, so it isn’t possible to pass an variable to a function and have it assigned a new value within the function, including passing in an immutable primitive type value and having it replaced with a modified value.
It is possible to do something similar though by passing in the value inside a data structure or other object.
For example, in the following program a string has its value modified in two different ways. Firstly, a class object is used to store the string’s value, and secondly, a list is used for the same purpose.
class Wrapper(object): def __init__(self, value): self.value = value def pass_by_reference1(wrapper): wrapper.value = wrapper.value + ", and spam" def pass_by_reference2(wrapper): wrapper = wrapper + ", and spam" def main(): var1 = Wrapper("A string"); pass_by_reference1(var1) print var1.value var2 = ["Another string"] pass_by_reference2(var2) print var2 if __name__ == '__main__': main()