Is it expected that nested variables in Python overlaps? for example:
for i in range(1,10):
x = [0xFF for i in range(6)]
print(i)
what is the expected result (sequence) ? With Python 2.7 I'm getting nine fives.
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4 Answers
What you see is a side-effect of using list comprehensions. The iterator variable inside the list comprehension is identical with the one of the for loop. This means that the iterator variable of the list comprehension is not local the expressions itself.
Example:
>>> [x for x in range(10)]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> print x
9
So both iterator variable names should be distinct.
Comments
Python does not have block scope. So variables you change inside a block will be visible outside that block. Only classes, functions and modules create scopes.
Comments
i will be pointing to the last element in range(6) i.e. 5, when you are printing it
when the list comprehension completes the value of i is 5, which is what you get while printing
your external loop runs for range(1,10) i.e. 9 times
In [47]: len(range(1,10))
Out[47]: 9
Comments
When you declare any variable it will be store the value. In python when you initialise any variable and store some value it will be available till the variable will not destroy. So when you write x = 10 inside the loop you will get the x out side the loop also. If you want to delete that variable then type del x then you will not get the value of the x
