Integer to "binary string"?

[darrell]

i=5
s = ''
while i:
    print 'S top: %4s I top: %d'%(s,i)
    s = (i & 1 and '1' or '0') + s # (i&1) is bitwise AND, so 5 & 1 is 1
    # If the result of i & 1 is 1 then add '1' to s
    i >>= 1 # right shift 1 and put the result back into 'i'
    print 'S bot: %4s I bot: %d'%(s,i)
    
print s

---Output
S top:      I top: 5
S bot:    1 I bot: 2
S top:    1 I top: 2
S bot:   01 I bot: 1
S top:   01 I top: 1
S bot:  101 I bot: 0
101

--Darrell



Gustaf Liljegren wrote:

> I'm writing a short program to help me understand certain concepts of the
> character encoding UTF-16. The script should be able to encode integers to
> strings of ones and zeros, to illustrate what happens during
> serialization.
> 
> I was hunting for a function to convert integers to these strings and vice
> versa, but found none. Then I hunted on Google and found:
> 
> def bin(i):
>      s = ''
>      while i:
>          s = (i & 1 and '1' or '0') + s
>          i >>= 1
>      return s or '0'
> 
> This works, but I don't understand it. Can anyone explain what happens on
> the three last rows? Also, can you show how to write a similar function
> for decoding?
> 
> Gustaf