Python - printing out list separated with comma
Pass sep=","
as an argument to print()
You are nearly there with the print statement.
There is no need for a loop, print has a sep
parameter as well as end
.
>>> print(*range(5), sep=", ")
0, 1, 2, 3, 4
A little explanation
The print
builtin takes any number of items as arguments to be printed. Any non-keyword arguments will be printed, separated by sep
. The default value for sep
is a single space.
>>> print("hello", "world")
hello world
Changing sep
has the expected result.
>>> print("hello", "world", sep=" cruel ")
hello cruel world
Each argument is stringified as with str()
. Passing an iterable to the print statement will stringify the iterable as one argument.
>>> print(["hello", "world"], sep=" cruel ")
['hello', 'world']
However, if you put the asterisk in front of your iterable this decomposes it into separate arguments and allows for the intended use of sep
.
>>> print(*["hello", "world"], sep=" cruel ")
hello cruel world
>>> print(*range(5), sep="---")
0---1---2---3---4
Using join
as an alternative
The alternative approach for joining an iterable into a string with a given separator is to use the join
method of a separator string.
>>>print(" cruel ".join(["hello", "world"]))
hello cruel world
This is slightly clumsier because it requires non-string elements to be explicitly converted to strings.
>>>print(",".join([str(i) for i in range(5)]))
0,1,2,3,4
Brute force - non-pythonic
The approach you suggest is one where a loop is used to concatenate a string adding commas along the way. Of course this produces the correct result but its much harder work.
>>>iterable = range(5)
>>>result = ""
>>>for item, i in enumerate(iterable):
>>> result = result + str(item)
>>> if i > len(iterable) - 1:
>>> result = result + ","
>>>print(result)
0,1,2,3,4
You can use str.join()
and create the string you want to print and then print it. Example -
print(','.join([str(x) for x in range(5)]))
Demo -
>>> print(','.join([str(x) for x in range(5)]))
0,1,2,3,4
I am using list comprehension above, as that is faster than generator expression , when used with str.join
.
To do that, you can use str.join()
.
In [1]: print ','.join(map(str,range(5)))
0,1,2,3,4
We will need to convert the numbers in range(5)
to string first to call str.join()
. We do that using map()
operation. Then we join the list of strings obtained from map()
with a comma ,
.