My notes & review of Py Donts by Rodrigo Girão Serrão

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Notes

Zip Up

• zip goes until the shortest of the iterators provided
• In Python 3.10> you can use a strict keyword to error if the length of iterators don’t match

firsts = ["Tyler", "Chandra"]
lasts = ["Hillery", "Hillery", "Hill"]

try:
    for z in zip(firsts, lasts, strict=True):
        print(z)
except Exception as e:
    print(e)

('Tyler', 'Hillery')
('Chandra', 'Hillery')
zip() argument 2 is longer than argument 1

• The error doesn’t occur until the end when the mismatch occurs because zip is lazily evaluated
• Interesting, you can use zip inside dict to make key,value pair of the iterators passed in

Chaining comparison operators

• Pitfall to watch out for is chaining != together.

a = c = 1
b = 2
if a != b != c:
    print("a, b, and c are all different: ", a, b, c)

a, b, and c are all different:  1 2 1

• a != b != c really evaluates to a != b and b != c it doesn’t tell you anything about a relates to c. Stick with chaining comparison operators on transitive operations

Boolean short-circuiting