【Python】Python十进制转二进制，可指定位数

# convert a decimal (denary, base 10) integer to a binary string (base 2)# tested with Python24   vegaseat    6/1/2005def Denary2Binary(n):    '''convert denary integer n to binary string bStr'''    bStr = ''    if n < 0:  raise ValueError, "must be a positive integer"    if n == 0: return '0'    while n > 0:        bStr = str(n % 2) + bStr        n = n >> 1    return bStrdef int2bin(n, count=24):    """returns the binary of integer n, using count number of digits"""    return "".join([str((n >> y) & 1) for y in range(count-1, -1, -1)])# this test runs when used as a standalone program, but not as an imported module# let's say you save this module as den2bin.py and use it in another program# when you import den2bin the __name__ namespace would now be  den2bin  and the# test would be ignoredif __name__ == '__main__':    print Denary2Binary(255)  # 11111111        # convert back to test it    print int(Denary2Binary(255), 2)  # 255        print        # this version formats the binary    print int2bin(255, 12)  # 000011111111    # test it    print int("000011111111", 2)  # 255        print    # check the exceptions    print Denary2Binary(0)    print Denary2Binary(-5)  # should give a ValueError#该代码片段来自于: http://www.sharejs.com/codes/python/5746