python for loop

Question

so evidently you write for loops in python int he following:

for i in range(1, 5):
    print i

but what if I'm actually using i as a counting trick and I specifically wanna do something like:

for (int i = 100; i > 20; i--)

or

for (int i = 0; i < 20 ; i += 2)

do you seriously have to write this in the body of the loop rather than the signature....

If you're using Python 2, use xrange instead of range in for loops (and anywhere else you don't actually need the whole range as a list). — David Z
– David Z, Commented Mar 16, 2011 at 3:58
While both of your examples can be trivially done with range(), in practice you will find that you should very rarely use it when you write for loops in Python. — Duncan
– Duncan, Commented Mar 16, 2011 at 8:53

wheaties · Accepted Answer · 2011-03-16 03:56:18Z

5

Different languages use different semantics to say the same thing. You can use the range function in several ways and it has as its arguments:

range(start, stop, jump)

So I can do

range(10, 1, -2)

to get a list like:

[10, 8, 6, 4, 2]

Using the three arguments of range you can get back to your counting tricks from C#, C++, C or Java.

answered Mar 16, 2011 at 3:56

wheaties

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Comments

dappawit · Accepted Answer · 2011-03-16 03:56:13Z

3

This should work:

for i in range(100,20,-1): 
    print i

and

for i in range(0, 20, 2): 
    print i

answered Mar 16, 2011 at 3:56

dappawit

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highBandWidth · Accepted Answer · 2011-03-16 03:56:36Z

1

You do something like this:

for i in range(100,20,-1):
   print i

or

for i in range(0,20,2):
   print i

answered Mar 16, 2011 at 3:56

highBandWidth

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