如何在Python中将过滤后的字符串追加到新列表中？

Question

我想在从旧列表中筛选出来的新列表中添加一个字符串。

到目前为止我尝试过的是：

languages = ['thai01', 'thai02', 'thai03', 'jap01', 'jap02', 'jap03']

thai = []
japanese = []


def filter_str(lang):
    if 'tha' in lang:
        return True
    else:
        return False


filter_lang = filter(filter_str, languages)
thai = thai.append(filter_lang)

print(thai)

我的预期产出是：

['thai01', 'thai02', 'thai03']

Answer 1

您可以使用列表理解：

languages = ['thai01', 'thai02', 'thai03', 'jap01', 'jap02', 'jap03']
thai = [x for x in languages if 'thai' in x]
print(thai)

产出：

['thai01', 'thai02', 'thai03']

若要帮助您理解这个oneliner的逻辑，请参阅以下基于代码的示例：

languages = ['thai01', 'thai02', 'thai03', 'jap01', 'jap02', 'jap03']

thai = []

def filter_str(lang):
    if 'tha' in lang:
        return True
    else:
        return False

for x in languages:
    if filter_str(x):
        thai.append(x)

print(thai)
# ['thai01', 'thai02', 'thai03']

for循环检查字符串'tha'是否发生(在本例中是在函数的帮助下)，它的逻辑与上面的列表理解相同(尽管对于第一个示例您甚至不需要这个函数)。您还可以结合您的功能使用列表理解：

languages = ['thai01', 'thai02', 'thai03', 'jap01', 'jap02', 'jap03']

def filter_str(lang):
    if 'tha' in lang:
        return True
    else:
        return False

thai = [x for x in languages if filter_str(x)]

print(thai)
# ['thai01', 'thai02', 'thai03']

Answer 2

您还可以在lambda函数中使用filter。

languages = ['thai01', 'thai02', 'thai03', 'jap01', 'jap02', 'jap03']
thai = list(filter(filter_str,languages))  # or  thai = list(filter(lambda x:'thai' in x,languages))

print(thai)    #['thai01', 'thai02', 'thai03']

或列表理解

thai = [y for y in languages if 'tha' in y]

Answer 3

执行下一步，而不是使用thai.append

thai.extend(filter(filter_str, languages))