Appending one string to another string in Python; In this tutorial, you will learn how to append one string to another string.
Python String Append
Python string object is immutable. So many time you use + operator to concatenate or join two strings in python programming and created a new string in python.
If you 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 join a string ‘n’ times:
def str_append(s, n):
output = ''
i = 0
while i < n:
output += s
i = i + 1
return output
Notice:- 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 join/concatenate string append operation is by creating a python list and appending strings to the python list. Then use python string join() function to join/merge string and list 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 examine these methods to make sure they are working as supposed.
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
A simple way to append strings in Python
You need to 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)'
