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
.
Another way to perform string append operation is by creating a list and appending strings to the list. Then use string join() function to merge them together to get the result string.
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)
Output:
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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from datetime import datetime start_time=datetime.now().strftime(“%H:%M”) flight_time=13.0987minutes k=start_time+flight time I need to add the current time and flight time could you please help me withs this?
- swathi meka