Loop over a collection using lambda expressions

A lambda expression is an anonymous function that can be conveniently used to traverse a collection. In this article, we will introduce how to use lambda expressions to iterate over collections, and provide specific code examples.

In Python, the syntax format of lambda expression is as follows:

lambda parameter list: expression

The parameter list of lambda expression can contain one or more parameters, Separate with commas. The expression is the return value of the lambda function.

Let's look at a simple example. Suppose there is a list containing integers. We want to traverse the list and print out each element.

numbers = [1, 2, 3, 4, 5]
    
# 使用lambda表达式遍历列表
for number in numbers:
    print(number)

The output result is:

1
2
3
4
5

In the above code, we use a for loop to traverse each element in the list, and then use the print function to print out the element.

In addition to using for loops, we can also use the built-in function map combined with lambda expressions to traverse the collection. The map function applies a lambda expression to each element of the collection and returns a new collection.

The following is an example of using map and lambda expressions to traverse a collection. We square all elements in a list.

numbers = [1, 2, 3, 4, 5]

# 使用map和lambda表达式遍历列表并平方
squared_numbers = list(map(lambda x: x**2, numbers))

print(squared_numbers)

The output result is:

[1, 4, 9, 16, 25]

In the above code, we use the map function and lambda expression to square each element in the list. Finally, we use the list function to convert the result into a new list and print it out.

In addition to using the map function, we can also use the filter function combined with lambda expressions to traverse the collection and filter out elements that meet certain conditions.

The following is an example of using filter and lambda expressions to traverse a collection. We filter out all even numbers in a list.

numbers = [1, 2, 3, 4, 5]

# 使用filter和lambda表达式遍历列表并筛选出偶数
even_numbers = list(filter(lambda x: x%2 == 0, numbers))

print(even_numbers)

The output result is:

[2, 4]

In the above code, we use the filter function and lambda expression to filter out even numbers in the list. Finally, we use the list function to convert the result into a new list and print it out.

Through the above code example, we can see the power of lambda expressions when traversing collections. It is concise and clear, and can help us complete traversal and filtering operations quickly.

In practical applications, we can flexibly use lambda expressions to traverse collections according to specific needs, thereby achieving more efficient and concise code.

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