Checking if strings are equal python

String Equals Check in Python: Using 4 Different Methods

In programming, string comparison is a fundamental operation used to determine whether two strings are equal.

Suppose you are building an application where you want to find a user using his/her username, the username stored in the database is a string and the keyword to be searched is also a string. So you would have to implement some functionality to detect that both strings are the same. Here comes the string comparison.

In this tutorial, we will learn how to compare strings using four different methods so you can choose any one as per your requirement.

Python String Comparison

In Python, string comparison is basically a process through which we compare the strings character-by-character to check for equality.

We can compare strings using several ways like using ‘==’ operator, ‘!=’ operator, ‘is’ operator and __eq__() function. Let’s look at them one by one.

Python ‘==’ Operator to Check the Equality of Two Strings

Python Comparison operators can be used to compare strings and check for their equality in a case-sensitive manner i.e. uppercase letters and lowercase letters would be treated differently.

Python ‘==’ operator compares the two strings in a character-by-character manner and returns True if both strings are equal, otherwise, it returns False.

s1 = "Python" s2 = "Python" s3 = "Java" print(s1 == s2) print(s1 == s3)

Here we can see that s1 is equal to another string s2 so True is printed to the console, whereas when we compared s1 with s3 we got False.

Python ‘!=’ Operator for String Comparison

Python ‘!=’ operator can also be used to perform a string equals check. Its return value is the opposite of the return value obtained using the ‘=’ operator.

The ‘!=’ operator compares two strings and returns True if the strings are unequal, otherwise, it returns False.

s1 = "Python" s2 = "Python" s3 = "Java" if(s1 != s3): print("s1 is not equal to s3") if(s1 != s2): print("s1 is not equal to s2") else: print("s1 is equal to s2")

s1 is not equal to s3 s1 is equal to s2

Python ‘is’ Operator for String Comparison

Python “is” operator can be used to efficiently check for the equality of two string objects. The “is” operator returns True if the two variables point to the same data object, else, it returns False.

s1 = "Python" s2 = "Python" s3 = "Java" if(s1 is s3): print("s1 is equal to s3") else: print("s1 is not equal to s3") if(s1 is s2): print("s1 is equal to s2") else: print("s1 is not equal to s2")

s1 is not equal to s3 s1 is equal to s2

Python __eq__() Function to perform String Equals Check

Python in-built __eq__() method can be used to compare two string objects. The __eq__() method basically compares two objects and returns a boolean True or False. It returns True if strings are equivalent, otherwise, it returns False.

str1 = "Python" str2 = "Python" str3 = "Java" if(str1.__eq__(str3)): print("str1 is equal to str3") else: print("str1 is not equal to str3") if(str1.__eq__(str2)): print("str1 is equal to str2") else: print("str1 is not equal to str2")

str1 is not equal to str3 str1 is equal to str2

String equals check in Python: Caseless Matching

If we use any of the above methods, they check the equality of strings using case-sensitive comparison. Let’s see with the help of an example.

str1 = "Python" str2 = "PYTHON" if(str1.__eq__(str2)): print("str1 is equal to str2") else: print("str1 is not equal to str2")

str1 is not equal to str2

As seen in the above example, the result turns out to be FALSE, because the comparison is case-sensitive.

So how can we check that strings are equal in a case-insensitive comparison?

In order to have a caseless string comparison, i.e. in a case-insensitive manner, we can use the Python string.casefold() function.

The string.casefold() function converts the string to lowercase instantly. It returns a casefolded copy of the string which can be used for caseless matching.

In this scenario of string comparison, we can pass both the input strings to the casefold() function. After which both the string will be converted to lowercase and thus, we can have a caseless comparison.

str1 = "Python" str2 = "PYTHON" str3 = "PYthoN" if((str1.casefold()).__eq__(str2.casefold())): print("str1 is equal to str2") else: print("str1 is not equal to str2") if((str1.casefold()) == (str3.casefold())): print("str1 is equal to str3") else: print("str1 is not equal to str3")

str1 is equal to str2 str1 is equal to str3

Conclusion

In this tutorial, we learned how to compare one string with another string in Python using four methods, and we have also implemented a case-insensitive approach to check string equality. The method mostly used by developers is the ‘==’ operator as it is very simple to implement and does the required job well. Hope you enjoyed reading our content.

References

Источник

Python String equals

While we believe that this content benefits our community, we have not yet thoroughly reviewed it. If you have any suggestions for improvements, please let us know by clicking the “report an issue“ button at the bottom of the tutorial.

Python strings equality can be checked using == operator or __eq__() function. Python strings are case sensitive, so these equality check methods are also case sensitive.

Python String equals

s1 = 'Apple' s2 = 'Apple' s3 = 'apple' # case sensitive equals check if s1 == s2: print('s1 and s2 are equal.') if s1.__eq__(s2): print('s1 and s2 are equal.') 

s1 and s2 are equal. s1 and s2 are equal. 

if s1 != s3: print('s1 and s3 are not equal') 

Python String equals case-insensitive check

Sometimes we don’t care about the case while checking if two strings are equal, we can use casefold() , lower() or upper() functions for case-insensitive equality check.

if s1.casefold() == s3.casefold(): print(s1.casefold()) print(s3.casefold()) print('s1 and s3 are equal in case-insensitive comparison') if s1.lower() == s3.lower(): print(s1.lower()) print(s3.lower()) print('s1 and s3 are equal in case-insensitive comparison') if s1.upper() == s3.upper(): print(s1.upper()) print(s3.upper()) print('s1 and s3 are equal in case-insensitive comparison') 

apple apple s1 and s3 are equal in case-insensitive comparison apple apple s1 and s3 are equal in case-insensitive comparison APPLE APPLE s1 and s3 are equal in case-insensitive comparison 

Python String equals with special characters

s1 = '$#ç∂' s2 = '$#ç∂' print('s1 == s2?', s1 == s2) print('s1 != s2?', s1 != s2) print('s1.lower() == s2.lower()?', s1.lower() == s2.lower()) print('s1.upper() == s2.upper()?', s1.upper() == s2.upper()) print('s1.casefold() == s2.casefold()?', s1.casefold() == s2.casefold()) 

s1 == s2? True s1 != s2? False s1.lower() == s2.lower()? True s1.upper() == s2.upper()? True s1.casefold() == s2.casefold()? True 

That’s all for checking if two strings are equal or not in Python. You can checkout complete script and more Python String examples from our GitHub Repository.

Thanks for learning with the DigitalOcean Community. Check out our offerings for compute, storage, networking, and managed databases. Learn more about us

Источник

Python Compare Strings – How to Check for String Equality

Ihechikara Vincent Abba

When crafting the logic in your code, you may want to execute different commands depending on the similarities or differences between two or more strings.

In this article, we’ll see various operators that can help us check if strings are equal or not. If two strings are equal, the value returned would be True . Otherwise, it’ll return False .

How to Check for String Equality in Python

In this section, we’ll see examples of how we can compare strings using a few operators.

But before that, you need to have the following in mind:

• Comparisons are case sensitive. G is not the same as g.
• Each character in a string has an ASCII value (American Standard Code for Information Interchange) which is what operators look out for, and not the actual character. For example, G has an ASCII value of 71 while g has a value of of 103. When compared, g becomes greater than G.

How to Compare Strings Using the == Operator

The == operator checks if two strings are equal. Here is an example:

We got a value of True returned because both strings above are equal.

Let’s make it look a bit more fancy using some conditional logic:

string1 = "Hello" string2 = "Hello" if string1 == string2: print("Both strings are equal") else: print("Both strings are not equal") # Both strings are equal

In the code above, we created two strings and stored them in variables. We then compared their values. If these values are the same, we would get one message printed to the console and if they aren’t the same, we would have a different message printed.

Both strings in our case were equal, so we had «Both strings are equal» printed. If we changed the first string to «hello», then we would have a different message.

Note that using = would make the interpreter assume you want to assign one value to another. So make sure you use == for comparison.

How to Compare Strings Using the != Operator

The != operator checks if two strings are not equal.

string1 = "Hello" string2 = "Hello" if string1 != string2: print("Both strings are not equal") # return if true else: print("Both strings are equal") # return if false # Both strings are equal

We’re using the same example but with a different operator. The != is saying the strings are not equal which is False so a message is printed based on those conditions.

I have commented the code to help you understand better.

How to Compare Strings Using the < Operator

This returns True because even though every other character index in both strings is equal, H has a smaller (ASCII) value than h .

We can also use conditional statements here like we did in previous sections.

How to Compare Strings Using the

Recall that this operator checks for two things – if one string is less or if both strings are the same – and would return True if either is true.

We got True because both strings are equal.

How to Compare Strings Using the > Operator

The > operator checks if one string is greater than another string.

Since the string on the left isn’t greater than the one on the right, we got False returned to us.

How to Compare Strings Using the >= Operator

The >= operator checks if one string is greater than or equal to another string.

Since one of both conditions of the operator is true (both strings are equal), we got a value of True .

Conclusion

In this article, we learned about the various operators you can use when checking the equality of strings in Python with examples. We also saw how case sensitivity can alter the equality of strings.

Источник