what is the cleanest way to loop in a range of numbers in python?

Question

So lets say

start = 10
end = 30

now I need a loop that goes from start to end

I was thinking of something like this:

for i in [start..end]
  print i

but that does not quite work. Is there a clean way to do this?

Answer 1

for i in range(start, end+1):
   print i

will give you the output from 10 to inclusive 30.

NOTE: The reason I added +1 to your end value is because the range() function specifies a half-closed interval . This means the first value is included , but the end value is not .

Ie,

  range(5, 10)

would give you a list of

  5, 6, 7, 8, 9

but not include 10.

You can also specify the step size for range() and a host of other things, see the documenation .

Finally, if you are using Python 2.x you can also use xrange() in place of range() , though in Python 3.x you will only have range() which is why I used it here.

If you are curious about the differences between range() and xrange() (though it is not really directly relevant to your question) the following two SO questions are a good place to start: What is the difference between range and xrange functions in Python 2.X? and Should you always favor xrange() over range()?

Answer 2

for i in xrange(start, end + 1):
    print i

Use range in xrange 's stead (as @Levon suggests) if you are using Python 3, as opposed to Python 2.x.

Answer 3

for i in xrange(10, 31):
   # something

Look at the fine manual, it'll explain it for you... Note that the ending point is "up to, but not including" - it's called a half closed range.

Also as others have mentioned in Python 3.x - range() is a generator and doesn't create a list as in Python 2.x. However, the 2to3 tool will automatically convert an xrange to a range statement.

In 2.x range generated a physical list which can be sliced etc... But in 3.x you have to write list(range(1000)) if you want it to materialise what it did in 2.x.

Answer 4

You're looking for range()

range(start,end) #end not inclusive
range(end) # starts with 0,end not inclusive
range(start, end, step) #increments of step, default = 1

For example,

for i in range(100,150):
   print i

Note: Py3k+ has only range(), prior versions have xrange() and range() , both are similar except xrange() is a generator, whereas range() creates a list of the numbers which you can iterate over.

Answer 5

You can iterate and print each element of the list. Try the following:

for i in range(start,end+1):
print i

Answer 6

您还可以通过打印从range返回的结果列表来打印全范围的数字：

print(range(start, end+1))