CODEWITHSUNDEEP
pythonbinarybit
APorter1031
APorter1031

Reputation: 2256

python bit_length() of 0 returns unexpected value

Why does the bit length of 0 return 0 and not 1?

>>> int(0).bit_length()
0

>>> int(2).bit_length()
2

2 in binary is 0x10 which represents two bits, doesn't zero in binary still techincally take up 1 bit since its representation in hex is 0x0?

Upvotes: 1

Views: 1406

Answers (2)

Weiner Nir
Weiner Nir

Reputation: 1475

Please read documentation on https://docs.python.org/3/library/stdtypes.html It is explained. That's how the function works. if you send it 0, it'll output 0

If x is zero, then x.bit_length() returns 0.

Upvotes: 0

Matt Hogan-Jones
Matt Hogan-Jones

Reputation: 3113

The Python documentation states

More precisely, if x is nonzero, then x.bit_length() is the unique positive integer k such that 2**(k-1) <= abs(x) < 2**k. Equivalently, when abs(x) is small enough to have a correctly rounded logarithm, then k = 1 + int(log(abs(x), 2)).
If x is zero, then x.bit_length() returns 0.

https://docs.python.org/3/library/stdtypes.html#int.bit_length

Upvotes: 2

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