Lambdas and sorting in Python

Tiny anonymous functions, mostly as sort keys.

books = [
    ("Dune", 1965),
    ("Neuromancer", 1984),
    ("Foundation", 1951),
]

by_year = sorted(books, key=lambda b: b[1])
by_title = sorted(books, key=lambda b: b[0].lower())
newest_first = sorted(books, key=lambda b: b[1], reverse=True)

double = lambda x: x * 2
titles = [b[0] for b in by_year]
longest = max(titles, key=len)

How it works

sorted with a key lambda orders books by year.
Another key sorts by lowercased title.
reverse=True flips the order; max with key=len picks.

Keywords and builtins used here

for
lambda
len
max
sorted

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Step 3 of 6 in Functions, step 35 of 72 in Language basics.

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