Is there any way to add one string to the end of another in python? e.g.
String1 = 'A' String2 = 'B'
and i want String3 == 'AB'
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Does this answer your question? Which is the preferred way to concatenate a string in Python?Vega– Vega2020-10-10 10:51:18 +00:00Commented Oct 10, 2020 at 10:51
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6 Answers
String concatenation in python is straightforward
a = "A"
b = "B"
c = a + b
print c
> AB
I benchmarked the three operations, performing 1m of each:
c = a + b
c = '%s%s' % (a,b)
c = "{0}{1}".format(a, b)
And the results are:
+: 0.232225275772
%s: 0.42436670365
{}: 0.683854960343
Even with 500 character strings, + is still fastest by far. My script is on ideone and the results (for 500 char strings) are:
+: 0.82
%s: 1.54
{}: 2.03
4 Comments
Utku Zihnioglu
And I always thought string concatenation with + sign was slow. Maybe because the strings are too short?
fredley
Maybe, I've uploaded my script to Ideone, where the results are even more pronounced: ideone.com/a6JMi
Curious2learn
I did not know .format method was slower than % method of formatting. I thought .format was the preferred method. Is it always slower?
fredley
Well for everything up to 500 character strings, yes. You can tweak my script to run further tests if you want.
You could use the simplest version: String3 = String1 + String2 or the format operator (deprecated in python3): String3 = '%s%s' % (String1, String2)
3 Comments
fredley
Since it's explicitly tagged python-3.x I'd remove that second option.
joaquin
@fredley, I read % would not be removed anytime soon. In the new python 3.2 it stays.
Greg Hewgill
For Python 3, you can use
String3 = "{0}{1}".format(String1, String2).In Python, the + operator concatenates strings:
>>> String3 = String1 + String2
>>> String3
'AB'
This is the simplest way and usually it's the right choice. However, sometimes you might need a more efficient string concatenation.
Comments
For simplicity when speed doesn't matter, you can't beat the ease of c=a+b. If speed does matter (because you're making a large number of successive concatenations, for example), str.join() can be a little more efficient (code at ideone).
+: 2.51
''.join([a,...z]): 0.2
append(): 2.05
From what I can tell, if you are making successive concatenations without touching the intermediate product, I'm better off appending each addition to a list, then joining everything at once. For the single concatenation case, a+b is still faster than a.join(b)
Comments
You can also try out str.join():
>>>s1='a'
>>>s2='b'
>>>s3=''.join((s1,s2))
>>>s3
'ab'
also if you write:
>>>s3='WhatEver'.join((s1,s2))
>>>s3
'aWhatEverb'
