遍历从 1 开始的范围的 Pythonic 方式

Question

Currently if I want to iterate 1 through n I would likely use the following method:

for _ in range(1, n+1):
    print(_)

Is there a cleaner way to accomplish this without having to reference n + 1 ?

It seems odd that if I want to iterate a range ordinally starting at 1, which is not uncommon, that I have to specify the increase by one twice:

1. With the 1 at the start of the range.
2. With the + 1 at the end of the range.

Answer 1

From the documentation:

range([start], stop[, step])

The start defaults to 0, the step can be whatever you want, except 0 and stop is your upper bound, it is not the number of iterations. So declare n to be whatever your upper bound is correctly and you will not have to add 1 to it.

eg

>>> for i in range(1, 7, 1): print(i)
... 
1
2
3
4
5
6
>>> for i in range(1, 7, 2): print(i)
... 
1
3
5

A nice feature, is that it works in reverse as well.

>>> for i in range(7, 0, -1): print(i)
... 
7
6
5
4
3
2
1

If you aren't using it as an index but for something that can have positive or negative values, it still comes in handy:

>>> for i in range(2, -3, -1): print(i)
... 
2
1
0
-1
-2
>>> for i in range(-2, 3, 1): print(i)
... 
-2
-1
0
1
2

Answer 2

range(1, n+1) is not considered duplication, but I can see that this might become a hassle if you were going to change 1 to another number.

This removes the duplication using a generator:

for _ in (number+1 for number in range(5)):
    print(_)

Answer 3

range(1, n+1) is common way to do it, but if you don't like it, you can create your function:

def numbers(first_number, last_number, step=1):
    return range(first_number, last_number+1, step)

for _ in numbers(1, 5):
    print(_)

Answer 4

Not a general answer, but for very small ranges (say, up to five), I find it much more readable to spell them out in a literal:

for _ in [1,2,3]:
    print _

That's true even if it does start from zero.

Answer 5

for i in range(n):
    print(i+1)

This will output:

1 
2
...
n