Stepping backwards in for loop?
Alex Martelli
aleaxit at yahoo.com
Sat Apr 14 10:30:36 EDT 2001
"Gustaf Liljegren" <gustafl at algonet.se> wrote in message
news:Xns9083A46CB3B93gustaflalgonetse at 194.213.69.152...
> Can't figure out how to step backwards, character by character in a
string.
> I was looking for a loop countruct with a counter to handle this, but the
> for loop in Python doesn't let me step backwards. What is the alternative?
You have several alternatives, such as:
thestr = 'ciao'
for x in range(len(thestr), 0, -1):
print thestr[x-1],
print
for x in range(len(thestr)):
print thestr[-x-1],
print
aulist = list(thestr)
aulist.reverse()
for c in aulist:
print c,
print
class Reverse:
def __init__(self, seq):
self.seq = seq
def __getitem__(self, index):
return self.seq[-index-1]
for c in Reverse('ciao'):
print c,
print
Each of these snippets will print 'o a i c'.
Alex
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