[Tutor] Equality of numbers and Strings
bgailer at gmail.com
Mon Jan 10 17:54:33 CET 2011
On 1/10/2011 11:07 AM, Karim wrote:
> Hello All,
> I am not a beginner in Python language but I discovered a hidden
> property of immutable elements as Numbers and Strings.
> s ='xyz'
> >>> t = str('xyz')
> >>> id(s) == id(t)
> Thus if I create 2 different instances of string if the string is
> identical (numerically).
Python "interns" certain literal strings - so a 2nd attempt to create
'xyz' will refer back to the original object.
I don't know all the rules - but the following program never prints n:
for n in range(1,10000):
s = eval("'" + 'wrtnjasdflkasjj'*n + "'")
t = eval("'" + 'wrtnjasdflkasjj'*n + "'")
if id(s) != id(t):
print n; break
whereas if I insert a ";" in the literal the program prints 1!
Also note str() returns the argument object unchanged.
Chapel Hill NC
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