when do two names cease to refer to the same string object?

John Salerno johnjsal at NOSPAMgmail.com
Fri Mar 3 02:45:10 CET 2006


To test this out a wrote a little script as an exercise:

for num in range(1, 10):
	x = 'c' * num
	y = 'c' * num
	
	if x is y:
	   print 'x and y are the same object with', num, 'characters'
	else:
	   print 'x and y are not the same object at', num, 'characters'
	   break

But a few questions arise:

1. As it is above, I get the 'not the same object' message at 2 
characters. But doesn't Python only create one instance of small strings 
and use them in multiple references? Why would a two character string 
not pass the if test?

2. If I say x = y = 'c' * num instead of the above, the if test always 
returns true. Does that mean that when you do a compound assignment like 
that, it's not just setting each variable to the same value, but setting 
them to each other?

Finally, I'd like to see how others might write a script to do this 
exercise. Basically I just wanted to see when two names stop referring 
to the same string, which I figured was based on length of the string. 
But I've also noticed that putting spaces in the string also affects 
things, so maybe there isn't just one way to test this.



More information about the Python-list mailing list