将二进制字符串转换为整数（Python）

Question

I have made the following code. The idea is that this binStrToInt actually recognizes my string as an integer, and can turn it into the actual number. My peers have pointed out that my code has a few errors. The only ones that I have noticed is that 1. math needs to be imported (for int) 2. return needs to be indented 3. num = num + int(binary_Str[i]) the i shouldn't be in that line? The issue: it just doesn't work. I have no idea what to do

def binStrToInt(binary_str):


    """The function binStrToInt() takes in one input, a string of ones and 
    zeros (no spaces) called BINARY_STR.  It treats that input as a binary 
    number (base 2) and converts it to a decimal integer (base 10). It 
    returns an integer result."""

    length = len(binary_str)

    num = 0
    for i in range(length)
        num = num + int(binary_Str[i])
        num = num * 2
return num / 2

Answer 1

It works fine when you remove all the typos and indentation problems:

def binStrToInt(binary_str):


    """The function binStrToInt() takes in one input, a string of ones and
    zeros (no spaces) called BINARY_STR.  It treats that input as a binary
    number (base 2) and converts it to a decimal integer (base 10). It
    returns an integer result."""

    length = len(binary_str)

    num = 0
    for i in range(length):
        num = num + int(binary_str[i])
        num = num * 2
    return num / 2

But honestly, how did you not see these? The interpreter tells you about most of them (all except the return indentation). And as commenters have mentioned, the built-in int() function will do the same thing if you pass it a string, and the number 2 to cause it to convert from a binary string.

EDIT Based on your comment below, you are somehow using a special quote, perhaps copied from a web-page or something. That won't work -- here is an example of something that worked and something that didn't in the interpreter:

>>> def binStrToInt(binary_str):
...     length = len(binary_str)
...     num = 0
...     for i in range(length):
...         num = num + int(binary_str[i])
...         num = num * 2
...     return num / 2
... 
>>> binStrToInt('101')
5
>>> binStrToInt(’101’)
  File "<stdin>", line 1
    binStrToInt(’101’)
                ^
SyntaxError: invalid syntax

Answer 2

You could make the logic a bit more easy to understand if you can re-write your code as

num = 0
for i in range(len(binary_str)):
    num = num * 2
    num = num + int(binary_str[i])
return num