The Python Apprentice

Managing resources with finally

One problem here is that our f.close() call was never executed.

To fix that, we can insert a try … finally block:

def read_series(filename):    try:        f = open(filename, mode='rt', encoding='utf-8')        series = []        for line in f:            a = int(line.strip())            series.append(a)    finally:        f.close()    return series

Now the file will always be closed, even in the presence of exceptions. Making this change opens up the opportunity for another refactoring: we can replace the for-loop with a list comprehension and return this list directly:

def read_series(filename):    try:        f = open(filename, mode='rt', encoding='utf-8')        return [ int(line.strip()) for line in f ]    finally:        f.close()

Even in this situation close() will still be called; the ...