python十进制转二进制_python十进制转二进制，可指定位数

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 6/1/2005

def 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 bStr

def 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 ignored

if __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

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