CODEWITHSUNDEEP
python-2.7radix
AlliDeacon
AlliDeacon

Reputation: 1495

Python 2.7 int(str, base) confusion

I am trying to use the int(x, base) class functionality using Python 2.7

when I do: num = int('100', 2) I receive the answer 4

however, when I do num = int('72', 2) I get the following traceback. 

Traceback (most recent call last):
  File "foobar1.py", line 26, in <module>
    num = int('72', 4)
ValueError: invalid literal for int() with base 4: '72'

I'm not sure what I'm missing.

Upvotes: 0

Views: 1267

Answers (3)

Laughing Vergil
Laughing Vergil

Reputation: 3756

The base number is specifying the numeric base of the value. For example, setting base to 16 means you are working with a hexadecimal number, while setting it to 8 means you are working with numbers in octal.

In octal (base 8), the digits available to you are 0--7. Trying to convert the number '89' using the function num = int('89', 8) will give you an error because the digits 8 and 9 are not used in base 8 numbers. Similarly, in base 2, the only digits available to you are 0 and 1 - the highest digit allowed will be the base number - 1.

Hopefully this clears things up.

Upvotes: 1

Minderov
Minderov

Reputation: 521

Second parameter means base. Base 2 means the number can use only 2 numbers (which are 0 and 1). When you are trying to convert 72 from binary (base 2) it fails because numbers 7 and 2 do not exist in binary.

If you are trying to convert your number to binary, use bin()

Upvotes: 1

Crowman
Crowman

Reputation: 25908

72 is not a binary number (at a minimum it's base 8), but when you specify a base of 2, you assert that it is. So your function fails.

num = int('1001000', 2)

or:

num = int('1020', 4)

would work as expected, for instance, and give you an integer that will be equivalent to decimal 72.

Upvotes: 1

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