String concatenation in a loop

Question

Here is my code, I want to do a conditional concatenation, my issue is that at the end of the for loop I have all variables starting with \n. To remove it I need to strip out each variable. I think there should be some batter way to handle this. Any suggestions would be appreciated.

foo = bar = remaining = ''
for i in ['foo', 'foo', 'hello', 'foo', 'tr', 'foo', 'bar', 'foo', 'el']:
    if 'foo' in i:
        foo += '\n%s' % i
    elif 'bar' in i:
        bar += '\n%s' % i
    else:
        remaining += '\n%s' % i
foo = foo.strip()
bar = bar.strip()
remaining = remaining.strip()

Why would you have difficulty removing the \n? Your own code is what places it in the output variables. There are a couple of ways you could tidy up that string concatenation to skip the newlines. — Heath Hunnicutt
– Heath Hunnicutt, Commented Sep 22, 2013 at 20:59
@HeathHunnicutt i would like to know some some batter approch to handle this, my code is fully funtional but i think i have done an extra code to handle this satutation — akhter wahab
– akhter wahab, Commented Sep 22, 2013 at 21:02

Eric · Accepted Answer · 2013-09-22 20:59:26Z

6

Instead of building strings, build lists and '\n'.join then when you finish:

foos = []
bars = []
remaining = []
for i in ['foo', 'foo', 'hello', 'foo', 'tr', 'foo', 'bar', 'foo', 'el']:
    if 'foo' in i:
        foos.append(i)
    elif 'bar' in i:
        bars.append(i)
    else:
        remaining.append(i)

foo = '\n'.join(foos)
bar = '\n'.join(bars)
remaining = '\n'.join(remaining)

answered Sep 22, 2013 at 20:59

Eric

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2 Comments

Eric Over a year ago

@HeathHunnicutt: Simultaneity is subjective. But yes, I'll admit this was low hanging fruit, and I should have got it right first time

user447688 Over a year ago

Hooray join(); much, much more efficient than successive concatenations

Siva Cn · Accepted Answer · 2013-09-26 19:13:19Z

0

foo = ''
bar = ''
remaining = ''

_list = ['foo', 'foo', 'hello', 'foo', 'tr', 'foo', 'bar', 'foo', 'el']

for outer in xrange(len(_list)):
    for i, e in enumerate(_list):

        foo += '\n%s' % _list.pop(i) if 'foo' in e else ''
        bar += '\n%s' % _list.pop(i) if 'bar' in e else ''

answered Sep 26, 2013 at 19:13

Siva Cn

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