Is defining a variable using a for loop possible in Python?

Question

If I'd want to do for i in range(10): x+= 1 it obviously wouldn't work since x is undefined, I'd have to declare x eg x=0 before trying to write to it, but now I have two lines, one for declaring x=0 and one for actually writing the data I want to x ( for i in range(10): x+= 1 ).

I was wondering, is there a way to do this in a single line? Or more specifically, declaring x as the result of a for loop?

Something along the lines of x = for i in range(10): x+= 1 ?

Would this even be possible or am I asking a nonsense question?

Answer 1

Not with a for statement.

However, you can use a similar construct, such as a list comprehension expression or a generator expression:

x = sum(i for i in range(10))

which is equivalent to just saying

x = sum(range(10))

Edit: as Dougal correctly notes, in your example you increment by 1, so the equivalent is

x = sum(1 for i in range(10))

which is in turn the same as x = len(range(10)) or just x = 10 .

Answer 2

In most cases, i would imagine you would just want to use x as the loop variable:

for x in range(10): pass#or range(1,11) 

An enumerate would also achieve a similar effect as what you are describing, assuming you want a different variable as the loop variable so as to do something else in the loop:

eg

for i,x in enumerate(range(x_start,x_end+1)): 
    #do something