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Python string object is immutable. So every time we use + operator to concatenate two strings, a new string is created. If we have to append many strings, using + operator will unnecessarily create many temporary strings before we have the final result.
Let’s look at a function to concatenate a string ‘n’ times.
def str_append(s, n): output = '' i = 0 while i < n: output += s i = i + 1 return output
Note that I am defining this function to showcase the usage of + operator. I will later use timeit module to test the performance. If you simply want to concatenate a string ‘n’ times, you can do it easily using
s = 'Hi' * 10.
def str_append_list_join(s, n): l1 =  i = 0 while i < n: l1.append(s) i += 1 return ''.join(l1)
Let’s test these methods to make sure they are working as expected.
if __name__ == "__main__": print('Append using + operator:', str_append('Hi', 10)) print('Append using list and join():', str_append_list_join('Hi', 10)) # use below for this case, above methods are created so that we can # check performance using timeit module print('Append using * operator:', 'Hi' * 10)
Append using + operator: HiHiHiHiHiHiHiHiHiHi Append using list and join(): HiHiHiHiHiHiHiHiHiHi Append using * operator: HiHiHiHiHiHiHiHiHiHi
I have both the methods defined in
string_append.py file. Let’s use timeit module to check their performance.
$ python3.7 -m timeit --number 1000 --unit usec 'import string_append' 'string_append.str_append("Hello", 1000)' 1000 loops, best of 5: 174 usec per loop $ python3.7 -m timeit --number 1000 --unit usec 'import string_append' 'string_append.str_append_list_join("Hello", 1000)' 1000 loops, best of 5: 140 usec per loop $ python3.7 -m timeit --number 1000 --unit usec 'import string_append' 'string_append.str_append("Hi", 1000)' 1000 loops, best of 5: 165 usec per loop $ python3.7 -m timeit --number 1000 --unit usec 'import string_append' 'string_append.str_append_list_join("Hi", 1000)' 1000 loops, best of 5: 139 usec per loop
If there are few strings, then you can use any method to append them. From a readability perspective, using + operator seems better for few strings. However, if you have to append a lot of string, then you should use the list and join() function.
You can checkout complete python script and more Python examples from our GitHub Repository.
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