Pass an argument to a function.

"""
Pass arguments to a function that tries to change them.
"""

import sys

def f(i, s, li0, li1):
    "Receive arguments and try to change their values."
    print(f'f received {i}, "{s}", {li0}, {li1}.')

    i = 20             #Put a new value into the variable i.
    s = "goodbye"      #Put a new value into the variable s.
    li0 = [10, 20, 30] #Put a new value into the variable li0.
    li1.append(30)     #Append a new value to the list to which the variable li1 refers.

    print(f'f changed them to {i}, "{s}", {li0}, {li1}.')
    print()


myInt = 10
myString = "hello"
myList0 = [10, 20]
myList1 = [10, 20]

f(myInt, myString, myList0, myList1)

print("After returning from the function,")
print(f"myInt = {myInt}")
print(f'myString = "{myString}"')
print(f"myList0 = {myList0}")
print(f"myList1 = {myList1}")

sys.exit(0)

The following output shows that the function f was able to change the contents of the list to which the variable myList1 refers. This variable li1 also refers to this list.

f received 10, "hello", [10, 20], [10, 20].
f changed them to 20, "goodbye", [10, 20, 30], [10, 20, 30].

After returning from the function,
myInt = 10
myString = "hello"
myList0 = [10, 20]
myList1 = [10, 20, 30]

Things to try

1. Pass a set to f and verify that f can change the contents of the set, just as f changed the contents of the list to which the variable myList1 refers. In general, f can change the contents of any argument that is a mutable collection. The mutable collections include list, set, dictionary, and others.