What is [2:] need for?

Question

In my code there is a line:

charInBinary = str(bin(ord(MESSAGE[i])))[2:]

What is [2:] need for?

If the output starts with `0b`, and you don't want that, you strip it off. — Mad Physicist, May 07 '22 at 16:05

score 2 · Answer 1 · answered May 07 '22 at 16:06

2

The [2: ] is slice notation, and since that's being performed on a str, it means that you're retrieving all of the characters of the string starting at index 2. In this case, that's getting rid of 0b.

answered May 07 '22 at 16:06

fireshadow52

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Thanks a lot that help me figure it out – Bảo Chi May 08 '22 at 02:32

score 0 · Answer 2 · answered May 07 '22 at 16:07

0

bin returns a string with a leading 0b prefix. The [2:] is snipping off the prefix, leaving only the binary digits

answered May 07 '22 at 16:07

pat

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score 0 · Answer 3 · answered May 07 '22 at 16:07

It's a simple question.

Without [2:] your output starts with 0b, So for removing this we use this [2:]

charInBinary = str(bin(ord(MESSAGE[i])))
print(charInBinary) # 0b111111

# WIth [2:]
charInBinary = str(bin(ord(MESSAGE[i])))[2:]
print(charInBinary) # 111111

What is [2:] need for?

3 Answers3