Python string contains ignore case

How to match a substring in a string, ignoring case

but no success for ignore case. I need to find a set of words in a given text file. I am reading the file line by line. The word on a line can be mandy, Mandy, MANDY, etc. (I don’t want to use toupper / tolower , etc.). I’m looking for the Python equivalent of the Perl code below.

10 Answers 10

If you don’t want to use str.lower() , you can use a regular expression:

import re if re.search('mandy', 'Mandy Pande', re.IGNORECASE): # Is True 

re.search(pattern, string, flags=0) docs.python.org/3/library/re.html#re.search Scan through string looking for the first location where the regular expression pattern produces a match, and return a corresponding match object. Return None if no position in the string matches the pattern; note that this is different from finding a zero-length match at some point in the string.

You are looking for the .lower() method:

string1 = "hi" string2 = "HI" if string1.lower() == string2.lower(): print("Equals!") else: print("Different!") 

Btw, There’s another post here. Try looking at this.

i know, i read, but the re.match and re.search solutions don’t check for special characters used in regex such as () or []

if you don’t really need to avoid it (for some reason like unicode), maching with lower() can be much more efficient than regex match.

One can use the in operator after applying str.casefold to both strings.

str.casefold is the recommended method for use in case-insensitive comparison.

Return a casefolded copy of the string. Casefolded strings may be used for caseless matching.

Casefolding is similar to lowercasing but more aggressive because it is intended to remove all case distinctions in a string. For example, the German lowercase letter ‘ß’ is equivalent to «ss». Since it is already lowercase, lower() would do nothing to ‘ß’; casefold() converts it to «ss».

The casefolding algorithm is described in section 3.13 of the Unicode Standard.

New in version 3.3.

For case-insensitive substring search:

needle = "TEST" haystack = "testing" if needle.casefold() in haystack.casefold(): print('Found needle in haystack') 

For case-insensitive string comparison:

a = "test" b = "TEST" if a.casefold() == b.casefold(): print('a and b are equal, ignoring case') 

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Python String Contains Substring Ignore Case: Methods and Functions

Learn different methods and functions to perform case-insensitive substring checks in Python. Check out the casefold(), lower(), in operator, str.contains method in pandas, re.findall() function, str.endswith() method, and StringUtils class in Java.

• The casefold() method
• The lower() method
• Using the in operator
• The str.contains method in pandas
• The re.findall() function
• The str.endswith() method
• Finding the index of a string in a list ignoring case
• The StringUtils class in Java
• Other simple code examples for ignoring case when checking if a string contains a substring in Python
• Conclusion
• How to check if a string contains a substring Python case-insensitive?
• Does string contain Ignorecase?
• How do you ignore a substring in Python?
• How to find a word in a string without case-sensitive Python?

Python is a popular programming language widely used for various purposes such as web development, data analysis, artificial intelligence, and automation. When working with strings, there may be times when we need to check if a string contains a substring in a case-insensitive manner. In this blog post, we will explore different methods and functions to perform case-insensitive substring checks in Python.

The casefold() method

The casefold() method is used to ignore cases when comparing strings in python. It performs a strict string comparison by removing all cases and performing a Unicode-based transformation. This method is similar to the lower() method, but it is more aggressive in removing any case distinctions that exist in a string.

Here is an example of using the casefold() method to compare two strings in a case-insensitive manner:

string1 = "Hello World" string2 = "hello world" if string1.casefold() == string2.casefold(): print("The strings are equal") 

The output of the above code will be:

The lower() method

The lower() method can also be used to convert strings to lowercase for comparison. It returns the lowercase equivalent of the string it is applied to. Here is an example of using the lower() method to compare two strings in a case-insensitive manner:

string1 = "Hello World" string2 = "hello world" if string1.lower() == string2.lower(): print("The strings are equal") 

The output of the above code will be:

Using the in operator

To check if a string contains a substring in a case-insensitive manner, we can convert both strings to lowercase using the lower() method and use the in operator to check if the substring is present. Here is an example:

string = "Hello World" substring = "world" if substring.lower() in string.lower(): print("The substring is present") 

The output of the above code will be:

The str.contains method in pandas

The str.contains method in pandas can be used to do a case-insensitive match in a pandas dataframe. It can be passed the case parameter as False to do a case-insensitive match. Here is an example:

import pandas as pddf = pd.DataFrame('col': ['Hello World', 'Foo Bar', 'Baz']>) substring = 'world' result = df['col'].str.contains(substring, case=False) print(result) 

The output of the above code will be:

0 True 1 False 2 False Name: col, dtype: bool 

The re.findall() function

The re.findall() function can take the re.IGNORECASE flag to do a case-insensitive search in a text. It returns a list of all non-overlapping matches of the pattern in the string. Here is an example:

import restring = 'Hello World, hello world' substring = 'world' result = re.findall(substring, string, flags=re.IGNORECASE) print(result) 

The output of the above code will be:

The str.endswith() method

The str.endswith() method can be used with the str.lower() method to perform a case-insensitive check for string endings. It returns True if the string ends with the specified suffix, else False . Here is an example:

string = 'Hello World' suffix = 'world' result = string.lower().endswith(suffix) print(result) 

The output of the above code will be:

Finding the index of a string in a list ignoring case

To find the index of a string in a list ignoring case, we can use a list comprehension to convert the strings in the list to lowercase. Here is an example:

list_of_strings = ['Hello World', 'Foo Bar', 'Baz'] substring = 'world' result = [i for i, s in enumerate(list_of_strings) if s.lower() == substring.lower()] print(result) 

The output of the above code will be:

The StringUtils class in Java

The StringUtils class has a containsIgnoreCase method to check if a string contains a substring while ignoring cases. It is a part of the Apache Commons Lang library in Java. Here is an example:

import org.apache.commons.lang3.StringUtils;public class Main  public static void main(String[] args)  String string = "Hello World"; String substring = "world"; boolean result = StringUtils.containsIgnoreCase(string, substring); System.out.println(result); > > 

The output of the above code will be:

Other simple code examples for ignoring case when checking if a string contains a substring in Python

In Python , for instance, python string contains substring ignore case code sample

string1 = "hi" string2 = "HI" if string1.lower() == string2.lower(): print "Equals!" else: print "Different!" 

Conclusion

Python provides different methods and functions to perform case-insensitive substring checks. The casefold() and lower() methods can be used to ignore cases when comparing strings. The in operator can be used to check if a substring is present in a case-insensitive manner. The str.contains method in pandas and the re.findall() function can be used for case-insensitive matches in dataframes and text, respectively. The str.endswith() method can be used to perform a case-insensitive check for string endings. The StringUtils class in Java provides a containsIgnoreCase method for case-insensitive substring checks. By using these methods and functions, we can easily perform case-insensitive substring checks in Python.

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String Contains Case Insensitive in Python

To check if a string contains a substring and ignore the case of the characters in the string, you can use the Python in operator and the lower() function.

s = "this IS a StrING" def containsCaseInsensitive(substring, string): if substring.lower() in string.lower(): return True else: return False print(containsCaseInsensitive("is",s)) print(containsCaseInsensitive("THIS",s)) print(containsCaseInsensitive("z",s)) #Output: True True False

You can also use the Python upper() function if you want.

s = "this IS a StrING" def containsCaseInsensitive(substring, string): if substring.upper() in string.upper(): return True else: return False print(containsCaseInsensitive("is",s)) print(containsCaseInsensitive("THIS",s)) print(containsCaseInsensitive("z",s)) #Output: True True False

When processing string variables, the ability to check certain conditions is valuable.

One such case is if you want to perform a case-insensitive search and see if a string is contained in another string if we ignore case.

In Python, we can create a contains case insensitive function easily with the Python in operator and the lower() function.

in in Python allows us to see if a string is contained in a string, but is case sensitive.

If you want to check if a string is contained in another and ignore case, we need to use lower() to convert both strings to lowercase.

Then you can see if the lowercase string is contained in the other lowercase string.

Below is an example showing you how to see if a string is contained in another string ignoring case in Python.

s = "this IS a StrING" def containsCaseInsensitive(substring, string): if substring.lower() in string.lower(): return True else: return False print(containsCaseInsensitive("is",s)) print(containsCaseInsensitive("THIS",s)) print(containsCaseInsensitive("z",s)) #Output: True True False

Hopefully this article has been useful for you to check if a string contains another string case insensitive in Python.

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