Python中使用filter函数的10个示例

filter函数是Python内置的一个高阶函数，它接受一个函数和一个可迭代对象作为参数，然后返回一个根据函数筛选出来的新的可迭代对象。下面是10个使用filter函数的示例。

1. 过滤出偶数

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))
print(even_numbers)  # 输出：[2, 4, 6, 8, 10]

2. 过滤出长度为3的字符串

words = ['apple', 'orange', 'banana', 'kiwi', 'grape']
filtered_words = list(filter(lambda x: len(x) == 3, words))
print(filtered_words)  # 输出：['kiwi']

3. 过滤出大于10的数

numbers = [1, 12, 5, 9, 15, 7, 18, 3, 21]
filtered_numbers = list(filter(lambda x: x > 10, numbers))
print(filtered_numbers)  # 输出：[12, 15, 18, 21]

4. 过滤掉小于零的数

numbers = [-1, 5, -3, 0, 8, -10, 2]
filtered_numbers = list(filter(lambda x: x >= 0, numbers))
print(filtered_numbers)  # 输出：[5, 0, 8, 2]

5. 过滤出奇数

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
odd_numbers = list(filter(lambda x: x % 2 != 0, numbers))
print(odd_numbers)  # 输出：[1, 3, 5, 7, 9]

6. 过滤出首字母为'a'的单词

words = ['apple', 'orange', 'banana', 'kiwi', 'grape']
filtered_words = list(filter(lambda x: x[0] == 'a', words))
print(filtered_words)  # 输出：['apple']

7. 过滤出包含元音字母的单词

words = ['apple', 'orange', 'banana', 'kiwi', 'grape']
vowels = ['a', 'e', 'i', 'o', 'u']
filtered_words = list(filter(lambda x: any(vowel in x for vowel in vowels), words))
print(filtered_words)  # 输出：['apple', 'orange', 'kiwi', 'grape']

8. 过滤出长度大于5并且包含字母'm'的单词

words = ['apple', 'orange', 'banana', 'kiwi', 'grape']
filtered_words = list(filter(lambda x: len(x) > 5 and 'm' in x, words))
print(filtered_words)  # 输出：['banana']

9. 过滤出能被3整除的数

numbers = [1, 3, 5, 9, 12, 15, 21]
filtered_numbers = list(filter(lambda x: x % 3 == 0, numbers))
print(filtered_numbers)  # 输出：[3, 9, 12, 15, 21]

10. 过滤掉空字符串

words = ['', 'apple', 'orange', '', 'banana']
filtered_words = list(filter(lambda x: x != '', words))
print(filtered_words)  # 输出：['apple', 'orange', 'banana']

以上是10个使用filter函数的示例，它们展示了如何使用filter函数根据特定的条件对可迭代对象进行过滤。根据实际的需求，通过定义不同的lambda函数和不同的条件，可以灵活地使用filter函数进行数据筛选和处理。