Count occurrences of a substring in a list of strings

You can do this by using the sum built-in function. No need to use list.count as well:

>>> data = ["the foo is all fooed", "the bar is all barred", "foo is now a bar"]
>>> sum('foo' in s for s in data)
2
>>>

This code works because booleans can be treated as integers. Each time 'foo' appears in a string element, True is returned. the integer value of True is 1. So it's as if each time 'foo' is in a string, we return 1. Thus, summing the 1's returned will yield the number of times 1 appeared in an element.

A perhaps more explicit but equivalent way to write the above code would be:

>>> sum(1 for s in data if 'foo' in s)
2
>>> 

You can try this:

from itertools import chain

data = ["the foo is all fooed", "the bar is all barred", "foo is now a bar"]

data = list(chain.from_iterable([i.split() for i in data]))

print(data.count("foo"))

Output:

2