Permutations of a string how to#
Permutations of a string code#

Permutations of a string how to#

In this post, you learned how to use Python to generate a list of all permutations of a string. Want to learn more about Python for-loops? Check out my in-depth tutorial that takes your from beginner to advanced for-loops user! Want to watch a video instead? Check out my YouTube tutorial here. We can also see here that we have many times more combinations when we use repetition than if we do not.

Permutations of a string code#

The code above can become quite resource intensive. In the code above, we use a for loop and a list comprehension to return all combinations of a Python string with repetition. Let’s take a look at an example, using the same string that we have used before, 'abc': # Use Python to get all combinations of a string with repetitionįinal_list = for x in final_list for y in i] This can be easily done using a Python for loop. In this section, you’ll learn how to use Python to get all permutations of a string with repetition. In the examples above, we used Python to find all combinations of a string without repetition. Permutations with Repetition of a String in Python Want to learn how to use the Python zip() function to iterate over two lists? This tutorial teaches you exactly what the zip() function does and shows you some creative ways to use the function. This method, however, is helpful for when you cannot use itertools for some reason. However, it is a bit less intuitive to follow along for beginner Python users, so perhaps using the itertools method might be preferred for readability. We can see that this returns the same as above. Words_list, words_list = words_list, words_list Let’s take a look at how this recursive method works to help find all combinations of a string in Python: # Getting all permutations of a string using recursion in Python The idea is that we backtrack for each possible combination that can exist. The concept we’ll use in recursion to create permutations is known as backtracking. Use Recursion in Python to Find All Permutations of a String More of a visual learner, check out my YouTube tutorial here. Want to learn more about Python list comprehensions? Check out this in-depth tutorial that covers off everything you need to know, with hands-on examples. In the next section, you’ll learn how to use recursion to find combinations of a string in Python.

Finally, we used a list comprehension to combine our permutations into individual strings.

We turned this object into a list, which returned a list of tuples, containing our permutations.

We then used the permutations() function to create a itertools object.We loaded our string and assigned it to the variable a_string.Let’s take a look at what we’ve done here: String_permutations = list(string_permutations) String_permutations = itertools.permutations(a_string) Let’s take a look at our example string and how we can use the itertools library to calculate its permutations: import itertools We we pass in an iterable, in this case, a string, the function returns a list of all possible combinations. In fact, the itertools library has a function called permutations. Believe it or not, strings in Python are iterable objects! Because of this, we can easily iterate over our strings using the itertools library. Itertools is a fantastic, built-in Python tool that allows you to make easy work of problems involving iterables. Use Itertools in Python to Find All Permutations of a String Now that you have an understanding of what it means to generate all combinations of a string in Python, let’s see how we can easily generate the different permutations of a string. So, in our example of 'abc', we would calculate the value of 3!, which actually evaluates to 3x2x1 = 6. We can actually calculate the number of permutations a string will have for any length strength, by calculating the factorial of its length. We can see here, that we have a list that contains six items.

When we find all the permutations of this string, we return the following list. Let’s, for example, take a look at a string that takes up three letters: 'abc'. Permutations of a string refers to all the different orderings a string may take.

Permutations with Repetition of a String in Python.

Use Recursion in Python to Find All Permutations of a String.

Use Itertools in Python to Find All Permutations of a String.