Asssume I have a function in python which returns the power of 2 of its input
def f(x):
return x**2
Assume also I have a vector of integers 1,2,3,4,5
I = asarray(list(range(1,6)))
Now I want to evaluate the function f with all inputs from I and the results should be in a vector of dimensions 5 (A 1x5 array in Python). My desired result is then: [1,4,9,16,25].
Can I get this result WITHOUT the use of a for or any other loop?
I have used array package
directly from the pythontips website...
use the map function!
squared = list(map(lambda x: x**2, I))
if you want to use your function inside the map-function, just do squared = list(map(f, I)).
There are generally two classical ways to apply a function to all elements of an iterable and store the results in a list. The more flexible one is a list comprehension:
result = [f(x) for x in range(1, 6)] # the upper bound is exclusive!
The other option is map which allows a more concise notation, in particular if you have a named function available and do not need to use a lambda or the like:
result = map(f, range(1, 6)) # Python2: returns list
result = list(map(f, range(1, 6))) # Python3: return iterator, so cast