Generator Expressions vs. List Comprehension

Question

When should you use generator expressions and when should you use list comprehensions in Python?

# Generator expression

(x*2 for x in range(256))

# List comprehension

[x*2 for x in range(256)]

Answer 1

The generator expression should be used if you're iterating once over anything. But in case if you want to store and use the generated results, then you're advised to use a list comprehension.

The main reason for choosing among one of these is the performance, so it is advised not to worry about performance you can pick anyone. 

def gen():

return (something for something in get_some_stuff())

print(gen()[:2])# generators don't support indexing 

print([5,6] + gen()) # generators can't be added to lists