with filter()

Introduction:

In Python, you can use a lambda function in a filter() function to filter elements based on a condition defined in the lambda function. The filter() function returns an iterator that passes elements through the lambda function and includes only those for which the condition is true.

Example:

Consider the following lambda function with filter():
python
```
filter(lambda x: x % 2 == 0, my_list)
```
- This lambda function filters out only the even numbers from the list my_list.

Observation:

The lambda function used in the filter() must return a boolean value, indicating whether each element should be included in the resulting list.

Examples:

Filter Even Numbers in a List Using a Lambda Function:

This example defines a lambda function in the filter() to filter out only even numbers from the list my_list.

Python Program:

python

my_list = [1, 2, 7, 4, 6, 9, 12, 16, 3]

# Lambda function with filter()
result = filter(lambda x: x % 2 == 0, my_list)

# Converting the returned iterable to a list
result = list(result)

print(result)

Output:
```
[2, 4, 6, 12, 16]
```

Filter Non-Empty Strings Using Lambda Function with filter():

This example defines a lambda function with filter() that filters out only non-empty strings from the given list of strings my_list.

Python Program:

python

my_list = ['apple', '', '', 'banana', 'cherry', '']

# Lambda function with filter()
result = filter(lambda x: len(x) != 0, my_list)

# Converting the returned iterable to a list
result = list(result)

print(result)

Output:
```
['apple', 'banana', 'cherry']
```

Exercises:

Filter Odd Numbers:

Define a lambda function in the filter() to filter out only odd numbers from a given list.

python

my_list = [1, 2, 7, 4, 6, 9, 12, 16, 3]

result = filter(lambda x: x % 2 != 0, my_list)
result = list(result)

print(result)  # Output: [1, 7, 9, 3]

Filter Positive Numbers:

Define a lambda function in the filter() to filter out only positive numbers from a given list.

python

my_list = [-1, 2, -7, 4, -6, 9, -12, 16, 3]

result = filter(lambda x: x > 0, my_list)
result = list(result)

print(result)  # Output: [2, 4, 9, 16, 3]

Filter Strings Longer Than 3 Characters:

Define a lambda function in the filter() to filter out only strings longer than 3 characters from a given list of strings.

python

my_list = ['apple', 'cat', 'banana', 'dog', 'cherry']

result = filter(lambda x: len(x) > 3, my_list)
result = list(result)

print(result)  # Output: ['apple', 'banana', 'cherry']

Summary:

In this tutorial, we learned how to use a lambda function with filter() to filter elements based on a condition. The filter() function is useful for creating concise and readable code when working with collections. Practice using lambda functions with filter() to get comfortable with these powerful tools in your Python programs!