Membership Operators

Membership Operators

Membership operators test whether something appears inside a collection: in and not in.

in

fruits = ["apple", "banana"]
print("banana" in fruits)     # True
print("grape" in fruits)      # False

Works on strings too

txt = "The best things in life are free!"
print("free" in txt)  # True

not in

print("grape" not in fruits)  # True
print("banana" not in fruits) # False

Works on any collection

• strings, lists, tuples, sets, dictionaries (checks keys), ranges.

print(3 in (1, 2, 3))     # True
print(2 in range(5))      # True
print("a" in {"a": 1})    # True (checks keys)

In an if

if "apple" in fruits:
    print("We have apples!")

TL;DR

• in returns True if a value is inside a collection.
• not in returns the opposite.
• Works on strings, lists, tuples, sets, dicts (keys), ranges.