Python apply function to list items

Apply Function to All Elements in List in Python

To apply a function to a list in Python, the easiest way is to use list comprehension to apply a function to each element in a list.

def add_one(x): return x + 1 example_list = [0, 1, 2, 3, 4, 5] print([add_one(i) for i in example_list]) #Output: [1, 2, 3, 4, 5, 6]

You can also use the map() function.

def add_one(x): return x + 1 example_list = [0, 1, 2, 3, 4, 5] print(list(map(add_one, example_list))) #Output: [1, 2, 3, 4, 5, 6]

When working with collections of data in Python, the ability to easily manipulate and change these collections can be very valuable.

One example of this might be if you have a function you want to apply to each of the elements of a list.

We can easily apply a function to all elements in a list.

The easiest way is with list comprehension.

Below is an example of how to use list comprehension to apply a function to a list.

def add_one(x): return x + 1 example_list = [0, 1, 2, 3, 4, 5] print([add_one(i) for i in example_list]) #Output: [1, 2, 3, 4, 5, 6]

Using map() to Apply a Function to a List in Python

The Python map() function is very useful and allows us to apply a function to a list.

To use map(), we just need to pass a function and a list to map, and then convert the returned value back to a list.

Below is a simple example of using map() to apply a function to a list of integers in Python.

def add_one(x): return x + 1 example_list = [0, 1, 2, 3, 4, 5] print(list(map(add_one, example_list))) #Output: [1, 2, 3, 4, 5, 6]

Using a Lambda Expression inside map() to Apply a Function to a List in Python

The map() function can take both regular functions and lambda functions. Let’s do the same operation as above but instead let’s use a lambda expression in map().

Below shows you how you can use a lambda function in map() to apply a function to a list in your Python code.

example_list = [0, 1, 2, 3, 4, 5] print(list(map(lambda x: x+1, example_list))) #Output: [1, 2, 3, 4, 5, 6]

Hopefully this article has been useful for you to learn how to apply functions to lists in your Python code.

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2.3.5. Apply Functions to Elements in a List#

2.3.5.1. any: Check if Any Element of an Iterable is True#

If you want to check if any element of an iterable is True, use any. In the code below, I use any to find if any element in the text is in uppercase.

text = "abcdE" any(c.isupper() for c in text) 

2.3.5.2. all: Check if All Elements of an Interable Are Strings#

If you want to check if all elements of an iterable are strings, use all and isinstance .

l = ['a', 'b', 1, 2] all(isinstance(item, str) for item in l) 

2.3.5.3. filter: Get the Elements of an Iterable that a Function Evaluates True#

If you want to get only the elements of an iterable that satisfy the given condition, use filter.

nums = [1, 2, 3, 4, 5] # Get even numbers list(filter(lambda num: num % 2 == 0, nums)) 

2.3.5.4. map method: Apply a Function to Each Item of an Iterable#

If you want to apply a function to each element of an iterable, use map .

nums = [1, 2, 3, 4, 5] # Multiply every number by 2 list(map(lambda num: num * 2, nums)) 

2.3.5.5. sort: Sort a List of Tuples by the First or Second Item#

If you want to sort a list of tuples by the first or second item in a tuple, use the sort method. To specify which item to sort by, use the key parameter.

prices = [('apple', 3), ('orange', 1), ('grape', 3), ('banana', 2)] # Sort by the first item by_letter = lambda x: x[0] prices.sort(key=by_letter) prices 

[('apple', 3), ('banana', 2), ('grape', 3), ('orange', 1)]

# Sort by the second item in reversed order by_price = lambda x: x[1] prices.sort(key=by_price, reverse=True) prices 

[('apple', 3), ('grape', 3), ('banana', 2), ('orange', 1)]

2.3.5.6. Use any and List Comprehension Instead of an If-Else Statement#

If you want to check whether a statement is True for one or more items in a list, using any and list comprehension is simpler than using a for-loop and an if-else statement.

FRUITS = ['apple', 'orange', 'grape'] def check_mention_fruit_1(text: str): for fruit in FRUITS: if fruit in text: return True check_mention_fruit_1('I got an apple.') 

def check_mention_fruit_2(text: str): return any(fruit in text for fruit in FRUITS) check_mention_fruit_2('I got an apple.') 

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Apply Function to Each Element of List in Python : Various Methods

List in python is a data structure that allows you to store multiple values in a single variable. It is mutable and can be added with other elements in the future using the append() method in python. Suppose you have a list and want to apply a function to each element of the list then How you can do so? In this entire post, you will know how to apply a function to each element of the list in python using different methods.

Methods to apply the function to each element of the list in python

Let’s explore all the methods that can help you to apply the function to each element in the list.

Method 1: Using the map() method

You can apply the function to each element of the list using the map() function. The map() function will accept your list and the function as arguments or parameters.

Suppose I have a function that squares each element of the list.

Now pass your list and function to the map() function to square each element of the list.

Method 2: Using for loop

The second method you can use is the for a loop. Here you will first create an empty list and add the squared elements to it after each iteration of the element.

Method 3: Pandas apply() function

You can apply a function to each element of the list in python using the panda’s module also. Here you will convert the list to dataframe and then apply the function on that using the apply() function.

Method 4: Using applymap() method

There is another function provided by the pandas module and it is applymap() method. This function will accept only the square function as an argument.

Output

Conclusion

As you can see, there are many ways to apply a function to each element of a list in Python. You can use a for loop, map, pandas apply, or applymap method. Each method has its own advantages and disadvantages. It’s up to you to choose the right method for your particular situation.

Источник

Apply Function to Each Element of List in Python : Various Methods

List in python is a data structure that allows you to store multiple values in a single variable. It is mutable and can be added with other elements in the future using the append() method in python. Suppose you have a list and want to apply a function to each element of the list then How you can do so? In this entire post, you will know how to apply a function to each element of the list in python using different methods.

Methods to apply the function to each element of the list in python

Let’s explore all the methods that can help you to apply the function to each element in the list.

Method 1: Using the map() method

You can apply the function to each element of the list using the map() function. The map() function will accept your list and the function as arguments or parameters.

Suppose I have a function that squares each element of the list.

Now pass your list and function to the map() function to square each element of the list.

Method 2: Using for loop

The second method you can use is the for a loop. Here you will first create an empty list and add the squared elements to it after each iteration of the element.

Method 3: Pandas apply() function

You can apply a function to each element of the list in python using the panda’s module also. Here you will convert the list to dataframe and then apply the function on that using the apply() function.

Method 4: Using applymap() method

There is another function provided by the pandas module and it is applymap() method. This function will accept only the square function as an argument.

Output

Conclusion

As you can see, there are many ways to apply a function to each element of a list in Python. You can use a for loop, map, pandas apply, or applymap method. Each method has its own advantages and disadvantages. It’s up to you to choose the right method for your particular situation.

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