Question

While going through the exercises, I came across something that, even after research, I simply cannot grasp.

Here’s the specific bit of code:

def print_all(f):
    print f.read()

For the whole script: http://learnpythonthehardway.org/book/ex20.html

What’s really, really confusing me is the (f) part.
Where does that f come from? What’s its purpose?

Oh well, thanks in advance!

Answer 1

f is an argument to the function, it is expected to be a file like object and is constructed with an open call in the example provided.

script, input_file = argv
#...
current_file = open(input_file) 
#...
#here, the body of current_file is executed, 
#with f replaced by the value of current_file
print_all(current_file)

where argv (provided by the sys module) is the list of strings provided on the commandline e.g. ["ex20.py", "test.txt"]