Adding a string to a Python variable

2 years ago

Olivia Parker

3 minutes

The Python string object cannot be changed after it is created. Therefore, when we use the + operator to combine two strings, a new string is generated each time. This means that if we need to add multiple strings together, using the + operator will result in the creation of several temporary strings before we obtain the desired final result.

Adding to a Python string

We’ll examine a function that combines a string ‘n’ times.

def str_append(s, n):
    output = ''
    i = 0
    while i < n:
        output += s
        i = i + 1
    return output

I am defining this function to demonstrate how to use the + operator. Later, I will use the timeit module to measure its performance. If you only want to repeat a string ‘n’ times, you can easily do it using s = ‘Hi’ * 10.

One alternative method for performing a string append operation involves creating a list and adding string elements to it. Afterwards, the string join() function can be utilized to combine these elements into a final string output.

def str_append_list_join(s, n):
    l1 = []
    i = 0
    while i < n:
        l1.append(s)
        i += 1
    return ''.join(l1)

We should assess these methods to ensure they function as anticipated.

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)

Can you provide one alternative formulation of the given sentence?

Result: Could you offer a single alternative statement?

Append using + operator: HiHiHiHiHiHiHiHiHiHi
Append using list and join(): HiHiHiHiHiHiHiHiHiHi
Append using * operator: HiHiHiHiHiHiHiHiHiHi

What is the most effective method for concatenating strings in Python?

I have the definitions of both methods in the string_append.py file. We can utilize the timeit module to examine 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

python string append, python add to string

Provide a single paraphrased version of the summary.

If there are only a few strings, you have the flexibility to use any method for joining them together. In terms of readability, using the + operator appears to be a better choice for a smaller number of strings. However, when dealing with a large number of strings that need to be appended, it is advisable to utilize the list and join() function.

You have the option to explore the entire Python script and additional Python examples on our GitHub Repository.