How to convert an integer to a string in any base?

Question

Python allows easy creation of an integer from a string of a given base via

int(str, base). 

I want to perform the inverse: creati

Answer 1

I know this is an old post, but I'm just leaving my solution here just in case.

def decimal_to_given_base(integer_to_convert, base):
     remainder = integer_to_convert // base
     digit = integer_to_convert % base
     if integer_to_convert == 0:
         return '0'
     elif remainder == 0:
         return str(digit)
     else:
         return decimal_to_given_base(remainder, base) + str(digit)

Answer 2

This is an old question but I thought i'd share my take on it as I feel it is somewhat simpler that other answers (good for bases from 2 to 36):

def intStr(n,base=10):
    if n < 0   : return "-" + intStr(-n,base)         # handle negatives
    if n < base: return chr([48,55][n>9] + n)         # 48 => "0"..., 65 => "A"...
    return intStr(n//base,base) + intStr(n%base,base) # recurse for multiple digits

Answer 3

Great answers! I guess the answer to my question was "no" I was not missing some obvious solution. Here is the function I will use that condenses the good ideas expressed in the answers.

• allow caller-supplied mapping of characters (allows base64 encode)
• checks for negative and zero
• maps complex numbers into tuples of strings

def int2base(x,b,alphabet='0123456789abcdefghijklmnopqrstuvwxyz'):
    'convert an integer to its string representation in a given base'
    if b<2 or b>len(alphabet):
        if b==64: # assume base64 rather than raise error
            alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
        else:
            raise AssertionError("int2base base out of range")
    if isinstance(x,complex): # return a tuple
        return ( int2base(x.real,b,alphabet) , int2base(x.imag,b,alphabet) )
    if x<=0:
        if x==0:
            return alphabet[0]
        else:
            return  '-' + int2base(-x,b,alphabet)
    # else x is non-negative real
    rets=''
    while x>0:
        x,idx = divmod(x,b)
        rets = alphabet[idx] + rets
    return rets

Answer 4

def base(decimal ,base) :
    list = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    other_base = ""
    while decimal != 0 :
        other_base = list[decimal % base] + other_base
        decimal    = decimal / base
    if other_base == "":
        other_base = "0"
    return other_base

print base(31 ,16)

output:

"1F"

Answer 5

Another short one (and easier to understand imo):

def int_to_str(n, b, symbols='0123456789abcdefghijklmnopqrstuvwxyz'):
    return (int_to_str(n/b, b, symbols) if n >= b else "") + symbols[n%b]

And with proper exception handling:

def int_to_str(n, b, symbols='0123456789abcdefghijklmnopqrstuvwxyz'):
    try:
        return (int_to_str(n/b, b) if n >= b else "") + symbols[n%b]
    except IndexError:
        raise ValueError(
            "The symbols provided are not enough to represent this number in "
            "this base")

Answer 6

"{0:b}".format(100) # bin: 1100100
"{0:x}".format(100) # hex: 64
"{0:o}".format(100) # oct: 144