Question

def checkCache(cachedText):
    for line in open("cache"):
        if cachedText + ":" in line:
            print line
            open("cache").close()
        else:
            requestDefinition(cachedText)

This code searches each line of a file (cache) for a specific string (cachedText + “:”).

If it does not find the specific string, within the entire file it is meant to call another function (requestNewDefinition(cachedText)).

However my above code executes the function for each non-matching line.

How can one search a file for a string (cachedText + “:”), and if the string is not found anywhere in the file, execute another function?

Example Cache:

hello:world
foo:bar

Answer 1

your for loop is broken. you are actually checking each line of the file and executing the function for each line which does not match.

note also that calling open("cache").close() will reopen the cache file and close it immediately, without closing the handle which was open at the beginning of the for loop.

one way to perform what you need is to make the else clause part of the for loop. beware that an else in a for loop is tricky !.

def checkCache(cachedText):
    cache = open( "cache" )
    for line in cache:
        if cachedText + ":" in line:
            break
    else:
        requestDefinition(cachedText)
    cache.close()

the else part of a for loop executes at the end of the loop, only if no break was called in the loop.