Membership Operators

Membership operators test whether a value is in a sequence or collection.

Operator	Meaning	Example
in	value is present	"a" in "cat"
not in	value is absent	4 not in [1, 2, 3]

Example

text = "Hello world"
data = {1: "a", 2: "b"}

print("H" in text)        # True
print("hello" in text)    # False (case-sensitive)
print(1 in data)          # True (checks keys)
print("a" in data)        # False

Note

For dictionaries, in checks keys, not values.

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