Check substring in string python
In this guide, we'll take a look at how to check if a string contains a substring in Python. As usual, each approach we'll cover has different pros and cons. Show
The in OperatorThe easiest way to check if a Python string contains a substring is to use the The
This operator is shorthand for calling an object's
To avoid this, you'll first want to check whether it points to
The String.index() MethodThe String type in Python has a method called Check out our hands-on, practical guide to learning Git, with best-practices, industry-accepted standards, and included cheat sheet. Stop Googling Git commands and actually learn it! If the substring is not found, a
This method is useful if you need to know the position of the substring, as opposed to just its existence within the full string. The String.find() MethodThe String type has another method called If
If you'd prefer to avoid the need to catch errors, then this method should be favored over Regular Expressions (RegEx)Regular expressions provide a more flexible (albeit more complex) way to check strings for pattern matching. Python is shipped with a built-in module for regular expressions, called
This method is best if you are needing a more complex matching function, like case insensitive matching. Otherwise the complication and slower speed of regex should be avoided for simple substring matching use-cases. This article was written by Jacob Stopak, a software consultant and developer with passion for helping others improve their lives through code. Jacob is the creator of Initial Commit - a site dedicated to helping curious developers learn how their favorite programs are coded. Its featured project helps people learn Git at the code level.
99% of use cases will be covered using the keyword,
For the use case of getting the index, use
or
ExplanationUse the
The opposite (complement), which the original question asked for, is
This is semantically the same as Avoid using __contains__The "contains" method implements the behavior for
returns
But don't. Methods that start with underscores are considered semantically non-public. The only reason to use this is when implementing or extending the
and now:
Don't use find and index to test for "contains"Don't use the following string methods to test for "contains":
Other languages may have no methods to directly test for substrings, and so you would have to use these types of methods, but with Python, it is much more efficient to use the Also, these are not drop-in replacements for If you really mean Performance comparisonsWe can compare various ways of accomplishing the same goal.
And now we see that using
How can in be faster than __contains__ if in uses __contains__?This is a fine follow-on question. Let's disassemble functions with the methods of interest:
so we see that the How do you check if a substring is in a string Python?The in Operator
It returns a Boolean (either True or False ). To check if a string contains a substring in Python using the in operator, we simply invoke it on the superstring: fullstring = "StackAbuse" substring = "tack" if substring in fullstring: print("Found!") else: print("Not found!")
How do I check if a string contains a substring?You can use contains(), indexOf() and lastIndexOf() method to check if one String contains another String in Java or not. If a String contains another String then it's known as a substring. The indexOf() method accepts a String and returns the starting position of the string if it exists, otherwise, it will return -1.
How do you check if a word is present in a string in Python?We can iteratively check for every word, but Python provides us an inbuilt function find() which checks if a substring is present in the string, which is done in one line. find() function returns -1 if it is not found, else it returns the first occurrence, so using this function this problem can be solved.
How do you check whether a string contains a substring in pandas?Using “contains” to Find a Substring in a Pandas DataFrame
The contains method returns boolean values for the Series with True for if the original Series value contains the substring and False if not. A basic application of contains should look like Series. str. contains("substring") .
How do you check if a character is present in a string in Python?find() str. find() method is generally used to get the lowest index at which the string occurs, but also returns -1, if string is not present, hence if any value returns >= 0, string is present, else not present.
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