Challenge question question

Question

I came across this line of code in a challenge:
a = [i for i in range(1,4) if i%2==0]

I understand what the line does, but having difficulty understanding the section “i for i in range”. My initial thought is that “for i in range” should perform the task, but that gets an invalid syntax error.

Can someone please help with the logic?

Answer 1

This form is named list comprehension and is a special syntax in python. I mean you should memorize it as it exists:
[Variable; for variable in iterable; conditions]
Note that semicolon is for showing different sections not in the syntax.

Answer 2

This is a list comprehension:

a = [i for i in range(1,4) if i%2==0]

There is a for loop which gets input from a range object, namely numbers from 1 up to 3. Content of *for loop var i* will be appended to *list a*, but only if it's an even number. This is checked with *if i%2==0*. So result is 2, as this is the only even number in the defined range.

Answer 3

That helps to also explain why the scope of i is within the list comprehension. Once outside the variable no longer exists!

Thank you for the helpful explanations!!

Answer 4

i []
for i in range(1,4):
If i%2==0:
Print(i)