smashing tons of crap together isn't necessarily "highly proficient". In some cases it makes things harder to read and/or harder to maintain and many times certainly harder to edit.

True that. But there is also another side to this story, where such nested calls translates naturally to what we are thinking, i.e.

length(unique(text)) comes from the thought "How many(length()) unique (unique()) words are there in this text(text)?"

R version for comparison (;

    length(unique(scan('test.txt',character(),sep=" ")))

Very clean. 1 small change to make it count of frequencies-

table(scan('test.txt',character(),sep=" "))

Don't know when set comprehensions and resource handlers were introduced so that might not run everywhere

    def read_words(words_file):
        with open(words_file, 'r') as f:
            return {word for line in f for word in line.split()}

len(set(open("test.txt").read().split()))

Oh, I like this one. Not quite what OP asked, but very clean.

GP asked for counts, not uniques.

Oops, you're right.

    words = open("test.txt").read().split()
    [(k, len(list(g))) for k, g in groupby(words, lambda x: x)]

Doesn't that require an "import itertools"?

Yup. Sorry.

Oops, should have been this:

    words = open("test.txt").read().split()
    [(k, len(list(g))) for k, g in groupby(words, lambda x: x)]

except that's wrong, all you're doing is counting the number of unique words, and you didn't even consider Foo and foo as the same in your example. Part of proficiency is understanding the problem.