Get string in list python

Find a string in a List in Python

There are three ways to find a string in a list in Python. They’re as follows:

1. With the in operator in Python
2. Using list comprehension to find strings in a Python list
3. Using the any() method to find strings in a list
4. Finding strings in a list using the filter and lambda methods in Python

Let’s get right into the individual methods and explore them in detail so you can easily implement this in your code.

1. Using the ‘in’ operator to find strings in a list

In Python, the in operator allows you to determine if a string is present a list or not. The operator takes two operands, a and b , and the expression a in b returns a boolean value.

If the value of a is found within b , the expression evaluates to True , otherwise it evaluates to False .

Here, ret_value is a boolean, which evaluates to True if a lies inside b , and False otherwise.

Here’s an example to demonstrate the usage of the in operator :

a = [1, 2, 3] b = 4 if b in a: print('4 is present!') else: print('4 is not present')

To make the process of searching for strings in a list more convenient, we can convert the above into a function. The following example illustrates this:

def check_if_exists(x, ls): if x in ls: print(str(x) + ' is inside the list') else: print(str(x) + ' is not present in the list') ls = [1, 2, 3, 4, 'Hello', 'from', 'AskPython'] check_if_exists(2, ls) check_if_exists('Hello', ls) check_if_exists('Hi', ls)

2 is inside the list Hello is inside the list Hi is not present in the list

The in operator is a simple and efficient way to determine if a string element is present in a list. It’s the most commonly used method for searching for elements in a list and is recommended for most use cases.

2. Using List Comprehension to find strings

Let’s take another case, where you wish to only check if the string is a part of another word on the list and return all such words where your word is a sub-string of the list item.

List comprehensions can be a useful tool to find substrings in a list of strings. In the following example, we’ll consider a list of strings and search for the substring “Hello” in all elements of the list.

ls = ['Hello from AskPython', 'Hello', 'Hello boy!', 'Hi']

We can use a list comprehension to find all elements in the list that contain the substring “Hello“. The syntax is as follows:

ls = ['Hello from AskPython', 'Hello', 'Hello boy!', 'Hi'] matches = [match for match in ls if "Hello" in match] print(matches)

We can also achieve the same result using a for loop and an if statement. The equivalent code using a loop is as follows:

ls = ['Hello from AskPython', 'Hello', 'Hello boy!', 'Hi'] matches = [] for match in ls: if "Hello" in match: matches.append(match) print(matches)

In both cases, the output will be:

['Hello from AskPython', 'Hello', 'Hello boy!']

As you can observe, in the output, all the matches contain the string Hello as a part of the string. Simple, isn’t it?

3. Using the ‘any()’ method

The any() method in Python can be used to check if a certain condition holds for any item in a list. This method returns True if the condition holds for at least one item in the list, and False otherwise.

For example, if you wish to test whether ‘AskPython’ is a part of any of the items of the list, we can do the following:

ls = ['Hello from AskPython', 'Hello', 'Hello boy!', 'Hi'] if any("AskPython" in word for word in ls): print('\'AskPython\' is there inside the list!') else: print('\'AskPython\' is not there inside the list')

In the above example, the condition being checked is the existence of the string «AskPython» in any of the items in the list ls . The code uses a list comprehension to iterate over each item in the list and check if the condition holds.

If the condition holds for at least one item, any() returns True and the first if statement is executed. If the condition does not hold for any item, any() returns False and the else statement is executed.

'AskPython' is there inside the list!

4. Using filter and lambdas

We can also use the filter() method on a lambda function, which is a simple function that is only defined on that particular line. Think of lambda as a mini function, that cannot be reused after the call.

ls = ['Hello from AskPython', 'Hello', 'Hello boy!', 'Hi'] # The second parameter is the input iterable # The filter() applies the lambda to the iterable # and only returns all matches where the lambda evaluates # to true filter_object = filter(lambda a: 'AskPython' in a, ls) # Convert the filter object to list print(list(filter_object))

We do have what we expected! Only one string matched with our filter function, and that’s indeed what we get!

Conclusion

We have seen that there are various ways to search for a string in a list. These methods include the in operator, list comprehensions, the any() method, and filters and lambda functions. We also saw the implementation of each method and the results that we get after executing the code. To sum up, the method you use to find strings in a list depends on your requirement and the result you expect from your code. It could be a simple existence check or a detailed list of all the matches. Regardless of the method, the concept remains the same to search for a string in a list.

References

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5 Easy Ways to Find String in List in Python

We got to know about many topics in python. But have you ever tried to find the string in a list in Python? In this tutorial, we will be focusing on finding the string in a list. There are multiple ways through which we can find the string in a list. We will be discussing all of them in this article.

We will find the string in a python list with multiple ways like for loop, in operator, using count, any() function.

5 Ways With Examples to Find The String In List in Python

We will discuss how we can find the string in a list with examples explained in detail.

1. Using Simple For Loop

In this example, we will be making a list with elements of a string. We will then take an input string from the user, which we want to find that the string contains in a list. By using for loop, we will find the string in a list. Let us look in detail with the help of the example explained below:

#input list lst = ['abc', 'def', 'ghi','python', 'pool'] #input string from user str = input("Enter the input string : ") c = 0 #applying loop for i in lst: if i == str: c = 1 break if c == 1: print("String is present") else: print("String is not present")

Enter the input string : python String is present

Explanation:

• Firstly, we will make a list that will contain some element in the form of a string.
• Then, we will take the input from the user in the form of a string.
• We will take a variable c which is set to 0.
• After that, we will be applying for loop.
• Inside for loop, we will apply if condition in which we will check if the element of the list is equal to the string. If they are equal c value becomes 1, and the loop gets breaks.
• At last, we will check if c is equal to 1 or 0. if c is equal to 1, we will print string is present and if c == 0, we will print string is not present.
• Hence, you can see the output.

2. Using in operator to Find The String List in Python

It is the membership operator in python. It is used to test whether a value or variable is found in a sequence (string, list, tuple, set, and dictionary).

In this example, we will be making a list with elements of a string. We will apply in operator if we give the string to be searched and check if it is in the list. Let us look in detail with the help of the example explained below:

#input list lst = ['abc', 'def', 'ghi','python', 'pool'] #applying if condition if 'pool' in lst: print("string is present") else: print("string is not present") #checking false condition if 'pools' in lst: print("string is present") else: print("string is not present")

string is present string is not present

Explanation:

• Firstly, we will make a list that will contain some element in the form of a string.
• Then, we will apply the ‘in’ operator inside the if condition and check if the string we want to check is present in the given list or not.
• If the string is present, the output is printed as the string is present, and if the string is not present, the output is printed as the string is not present.
• We have taken both examples. One of the lists is present, and one of the lists is not present in the program.
• Hence, you can see the output.

3. Using count() function

The count() function is used to count the occurrences of a string in a list. If we get the output as 0, then it says that the string does not contain the list, and if the output is 1, then the string is present in the list.

In this example, we will be making a list with elements of a string. We will then take an input string from the user, which we want to find that the string contains in a list. Then, we will apply the count function passing the input string and see the count value through the if condition, and print the output.

#input list lst = ['abc', 'def', 'ghi','python', 'pool'] #input string from user str = input("Enter the input string : ") #count function count = lst.count(str) if count > 0: print("String is present") else: print("String is not present")

Enter the input string : ghi String is present

Explanation:

• Firstly, we will make a list that will contain some element in the form of a string.
• Then, we will take the input from the user in the form of a string.
• Then, we will apply the count() function, which will count the string’s occurrence in a list.
• If the count’s value is equal to 0, the output will be printed as the string is not present, and if the count is greater than 0, the output is printed as the string is present in the list.
• Hence, you can see the output.

4. Using any() function to Find String In List in Python

The any() function returns True if the string is present in a list. Otherwise, it returns False. If the list is empty, it will return False.

In this example, we will be making a list with elements of a string. We will apply if condition, and in that, we will apply any() function through which we can find the string in a list is present or not.

#input list lst = ['abc', 'def', 'ghi','python', 'pool'] if any("pool" in word for word in lst): print("string is present") else: print("string is not present")

Explanation:

• Firstly, we will make a list that will contain some element in the form of a string.
• Then, we will apply any() function inside the condition where we will give the string we have to find and apply for loop.
• If the function finds any same string as given, the output gets printed as the string is present, and if it does not find any such string, the output gets printed as a string is not present.
• Hence, you can finally see the output as the string is present as the pool is present in the list.

5. Finding all the indexes of a particular string

In this example, we will be making a list with elements of a string. Then, we will be selecting a particular string and try to find all the indexes at which the string is present. We will be using len() function for finding the length of the list and while loop for running the loop from starting till the end of the list.

#input list lst = ['A','D', 'B', 'C', 'D', 'A', 'A', 'C', 'D'] s = 'D' index = [] i = 0 length = len(lst) while i < length: if s == lst[i]: index.append(i) i += 1 print(f'is present in ')

Explanation:

• Firstly, we will make a list that will contain some element in the form of a string.
• Then, We will take a particular string of which we want to find the present indexes.
• After that, we will make an empty list as index and keep i=0.
• Then, we will calculate the length of the list.
• After that, we will apply while loop till the length of the list and check the condition if the string is preset at that index of list or not.
• If present we will store the index value in the new list index and continue the loop till the end.
• At last, we will print all the indexes.

Conclusion

In this tutorial, we have learned about how to find the string in a list. We have seen all the multiple methods through which we can find the string present in the list. We have also discussed all the methods with the examples explained in detail. You can use any of the methods according to your need in the program.

However, if you have any doubts or questions, do let me know in the comment section below. I will try to help you as soon as possible.

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