Question

How would you convert an arbitrary string into a unique integer, which would be the same across Python sessions and platforms? For example hash('my string') wouldn’t work because a different value is returned for each Python session and platform.

Answer 1

If a hash function really won’t work for you, you can turn the string into a number.

my_string = 'my string'
def string_to_int(s):
    ord3 = lambda x : '%.3d' % ord(x)
    return int(''.join(map(ord3, s)))

In[10]: string_to_int(my_string)
Out[11]: 109121032115116114105110103L

This is invertible, by mapping each triplet through chr.

def int_to_string(n)
    s = str(n)
    return ''.join([chr(int(s[i:i+3])) for i in range(0, len(s), 3)])

In[12]: int_to_string(109121032115116114105110103L)
Out[13]: 'my string'