What is the fastest way to replace elements in list?

[jacob l]

I am working with very large lists. I wish to replace elements satisfying a rule as quickly as possible.

For Example:

rule: if x < 0, replace with 0

Mylist: [1, 2, -4, -3, 4, -9]

Newlist: [1, 2, 0, 0, 4, 0]

I have Mylist and want to get Newlist. My best guess is to use enumerate, but not sure how to write this appropriately. Thanks

[dwblas]

Generally, it is faster to append to a new list. Also, take a look at the Python Style Guide when you have time. There are coding conventions that make code easier to read and understand when someone posts.

a_list = [1, 2, -4, -3, 4, -9]
b_list = []

for el in a_list:
    if el < 0:
        b_list.append(0)
    else:
        b_list.append(el)
print b_list