Reputation: 24334

For-loops in Python

What is the best way of doing this in Python?

for (v = n / 2 - 1; v >= 0; v--)

I actually tried Google first, but as far as I can see the only solution would be to use while.

Upvotes: 5

Answers (4)

Reputation: 49043

I would do this:

for i in reversed(range(n // 2)):
    # Your code
    pass

It's a bit clearer that this is a reverse sequence, what the lower limit is, and what the upper limit is.

Upvotes: 15

Reputation: 86146

for v in range(n//2, -1, -1)

However, in 90% of the cases when you would have used a for loop in C/Java/C#/VB, what you really want is list comprehension:

listOfStuff = [doSomethingWith(v) for v in range(n//2, -1, -1)]

Upvotes: 5

Reputation: 66043

for v in xrange(n/2 - 1, 0, -1):
   #your code here

Where v and n are ints or treated as ints. This means that the division will be an integer division, i.e., 1/2 == 0 is True.

Note: This is for Python 2.x .

Upvotes: 0

Reputation: 133503

The way to do it is with xrange():

for v in xrange(n // 2 - 1, -1, -1):

(Or, in Python 3.x, with range() instead of xrange().) // is flooring division, which makes sure the result is a whole number.

Upvotes: 13