Can we use contains for string in 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 I check if a string contains a string in Python?Using Python's "in" operator
The simplest and fastest way to check whether a string contains a substring or not in Python is the "in" operator . This operator returns true if the string contains the characters, otherwise, it returns false .
Can Python lists contain strings?Just like strings store characters at specific positions, we can use lists to store a collection of strings. In this tutorial, we will get a string with specific values in a Python list.
How do you check if a string contains a word Python?The simplest way to check if a string contains a substring in Python is to use the in operator. This will return True or False depending on whether the substring is found. For example: sentence = 'There are more trees on Earth than stars in the Milky Way galaxy' word = 'galaxy' if word in sentence: print('Word found.
How do you use contains in Python?The __contains__() method is a method of the Python String class that can be used to check whether the class contains another string or not.. my_string = 'welcome'. print("my string contains \'w\' =", my_string. ... . print("my string contains \'W\' =", my_string.. |