{"id":703,"date":"2018-04-29T06:47:45","date_gmt":"2018-04-29T06:47:45","guid":{"rendered":"http:\/\/www.afternerd.com\/blog\/?p=703"},"modified":"2020-05-25T13:16:00","modified_gmt":"2020-05-25T13:16:00","slug":"python-string-contains","status":"publish","type":"post","link":"https:\/\/www.afternerd.com\/blog\/python-string-contains\/","title":{"rendered":"How to Check if a Python String Contains Another String?"},"content":{"rendered":"

One of the most common operations that programmers use on strings is to check whether a string contains some other string.<\/p>\n

If you are coming to Python from Java, for instance, you might have used the contains<\/strong><\/a> method to check if some substring exists in another string.<\/p>\n

In Python, there are two ways to achieve this.<\/p>\n

First: Using the in operator<\/h2>\n

The easiest way is via Python’s in<\/span> operator.<\/p>\n

Let’s take a look at this example.<\/p>\n

>>> str = \"Messi is the best soccer player\"\r\n>>> \"soccer\" in str\r\nTrue\r\n>>> \"football\" in str\r\nFalse<\/code><\/pre>\n
As you can see, the in operator returns True when the substring exists in the string.<\/p>\n
Otherwise, it returns false.<\/p>\n
This method is very straightforward, clean, readable, and idiomatic.<\/p>\n
Second: Using the find method<\/h2>\n
Another method you can use is the string’s find method<\/a>.<\/p>\n
Unlike the in operator which is evaluated to a boolean value, the find<\/span> method returns an integer.<\/p>\n
This integer is essentially the index of the beginning of the substring if the substring exists, otherwise -1 is returned.<\/p>\n
Let’s see the find<\/span> method in action.<\/p>\n
>>> str = \"Messi is the best soccer player\"\r\n>>> str.find(\"soccer\")\r\n18\r\n>>> str.find(\"Ronaldo\")\r\n-1\r\n>>> str.find(\"Messi\")\r\n0<\/code><\/pre>\n
One cool thing about this method is you can optionally specify a start index and an end index to limit your search within.<\/p>\n
For example<\/p>\n
>>> str = \"Messi is the best soccer player\"\r\n>>> str.find(\"soccer\", 5, 25)\r\n18\r\n>>> str.find(\"Messi\", 5, 25)\r\n-1<\/code><\/pre>\n
Notice how a -1 was returned for “Messi”<\/span> because you are limiting your search to the string between indices 5 and 25 only.<\/p>\n
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Python 3 Cheat Sheet for Beginners<\/h2>\n
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