[Tutor] for/else question

[Michael Janssen]

On Thu, 11 Sep 2003, Gabriel Cooper wrote:

> So... yeah... Do /you/ use "else" with for loops? If so, when?

some time ago it has really helped me out of an ugly function:

def delpattern(inlist, patternl):
    """clean inlist from entries with certain sub-strings"""
    backl=[]
    for elem in inlist:
        for pattern in patternl:
            if elem.find(pattern) >-1:
                break
        else:
            backl.append(elem)
    return backl


#without for-if-else it would be (under the assumption you don't want
#to investigate further to get some clever list-comprehension or reg-exp
#solution):

def delpattern(inlist, patternl):
    """clean inlist from entries with certain sub-strings"""
    backl=[]
    for elem in inlist:
        found = 0
        for pattern in patternl:
            if elem.find(pattern) >-1:
                found = 1
                break # just to save time
        if not found:
            backl.append(elem)
    return backl

for-if-else seems much more readable (understandable) than
found-not-found to me. You have compared looking for something to doing
something. Here we're looking for something and only doing if not found.

Michael