Import Strategy

Import at Module Level

from math import sqrt  # compiles better

def compute(data):
    for x in data:
        yield sqrt(x)  # uses local sqrt

Avoid Imports Inside Loops

for x in data:
    import math  # slow!
    math.sqrt(x)

Lazy Imports for Optional Features

def optional_feature():
    import optional_module
    return optional_module.do()