Getting number of iteration

[Florian Lindner]

Hello,
when I'm iterating through a list with:

for x in list:

how can I get the number of the current iteration?

Thx,

Florian

 

[Bill Mill]

Hello,
when I'm iterating through a list with:

for x in list:

how can I get the number of the current iteration?

Python 2.4 and greater:

for n, x in enumerate(lst):
print "iteration %d on element %s" % (n, x)

Earlier:

n = 0
for x in lst:
print "iteration %d on element %s" % (n, x)
n += 1

And you shouldn't use list as a variable name; list() is a built-in
function which you'll clobber if you do.

Peace
Bill Mill
bill.mill at gmail.com

 

[Bill Mill]

Python 2.4 and greater:

ummm, make that 2.3 and greater. I always think things are more recent
than they are.

 

[George Sakkis]

Hello,
when I'm iterating through a list with:

for x in list:

how can I get the number of the current iteration?

Thx,

Florianfor

in python 2.3+:

for i,x in enumerate(sequence):
print "sequence[%d] = %s" %(i,x)


George

 

[Mike Meyer]

Earlier:

n = 0
for x in lst:
print "iteration %d on element %s" % (n, x)
n += 1

Just for the record, the old idiom was:

for n in xrange(len(lst)):
x = lst[n]
print "iteration %d on element %s" % (n, x)

<mike

 

[Fredrik Lundh]

n = 0
for x in lst:
print "iteration %d on element %s" % (n, x)
n += 1

Just for the record, the old idiom was:

for n in xrange(len(lst)):
x = lst[n]
print "iteration %d on element %s" % (n, x)

it was? of the following four solutions,

for n in xrange(len(lst)):
x = lst[n]
...

for n in range(len(lst)):
x = lst[n]
...

n = 0
for x in lst:
...
n += 1

for x, n in enumerate(lst):
...

the xrange solution tends to be the slowest, especially for
relatively short lists (up to a 1000 elements, or so).

the exact details vary somewhat between Python versions,
but the += solution is always a good choice, and the xrange
solution is almost always a bad choice.

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