JuniorCodeOccasional

What does `print(True + 4)` output, and why?

Predict the output and explain the type relationship behind it.

Python

print(True + 4)
print(True + True)
print(sum([True, False, True]))

Determine the output.

Prints 5, 2, 2. In Python bool is a subclass of int, with True == 1 and False == 0, so booleans participate directly in arithmetic. True + 4 is 1 + 4, and sum of booleans counts the True values. This is why summing a list of conditions counts how many are true.

Thinking bool is unrelated to int and cannot do arithmetic
Expecting True + 4 to raise a TypeError
Forgetting sum of booleans counts the True values

Why can True and 1 collapse to one key in a dict?
What does isinstance(True, int) return, and why?

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JuniorCodeOccasional

What does `print(True + 4)` output, and why?

Predict the output and explain the type relationship behind it.

Python

print(True + 4)
print(True + True)
print(sum([True, False, True]))

Determine the output.

Thinking bool is unrelated to int and cannot do arithmetic
Expecting True + 4 to raise a TypeError
Forgetting sum of booleans counts the True values

Why can True and 1 collapse to one key in a dict?
What does isinstance(True, int) return, and why?

Back to questions Open topic in roadmap →Answer it yourself — Quiz

What does print(True + 4) output, and why?

What does print(True + 4) output, and why?

What does `print(True + 4)` output, and why?

What does `print(True + 4)` output, and why?