Python Replace Example

Use the replace method to change a substring in a string into another substring.

Replace. A string cannot be changed in-place. We cannot assign characters. Instead we use the replace method to create a new string.Strings

With this method, we specify a substring that we want to replace, and another we want to replace it with. We can use an optional second argument.

First example. Let us begin with this simple example. Replace accepts two substring arguments: the "before" and "after" parts that are replaced.

And: The third argument is optional. It is a count. It indicates the maximum number of instances to replace.

Tip: Replace only handles substrings, not characters. If you need to replace many single characters, please consider the translate method.

Python program that uses replace value = "aabc" # Replace a substring with another. result = value.replace("bc", "yz") print(result) # Replace the first occurrence with a substring. result = value.replace("a", "x", 1) print(result) Output aayz xabc

Replace count. The third argument to replace() is optional. If we specify it, the replace method replaces that number of occurrences—this is a count argument.

Here: We have a string that says "cat cat cat" and we replace all occurrences, 0 occurrences, and 1 and 2 occurrences.

Python program that uses replace, count argument before = "cat cat cat" print(before) # Replace all occurrences. after = before.replace("cat", "bird") print(after) # Replace zero occurrences. # ... This makes no sense. after = before.replace("cat", "bird", 0) print(after) # Replace 1 occurrence. after = before.replace("cat", "bird", 1) print(after) # Replace first 2 occurrences. after = before.replace("cat", "bird", 2) print(after) Output cat cat cat bird bird bird cat cat cat bird cat cat bird bird cat

A note. Replace() is needed to change a part of string to a new string. If the index of the match is known, we could use two slices and then construct a new string with concatenation.Substring

A summary. With replace() we copy a string. The original is not changed. The copied string has the specified number of substrings replaced with a new substring (if found).
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