lambda — Advanced Examples

Creates a small anonymous (unnamed) function in a single expression

EasyIntermediateAdvancedExpert

Lambda closures and pitfalls

Understanding how lambda captures variables.

python
# Pitfall: lambda captures by reference, not value
funcs = [lambda: i for i in range(5)]
print([f() for f in funcs])  # All return 4!

# Fix: capture value with default argument
funcs = [lambda i=i: i for i in range(5)]
print([f() for f in funcs])  # Returns [0, 1, 2, 3, 4]

# Lambda in callbacks
handlers = {}
for event in ["click", "hover", "scroll"]:
    handlers[event] = lambda e=event: f"Handling {e}"

for name, handler in handlers.items():
    print(handler())

Lambda captures variables by reference, not by value. The default argument trick (lambda i=i: ...) forces capture at definition time.

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