检查Pandas DataFrame列中的字符串是否在字符串列表中

Question

如果我有这样一个框架

frame = pd.DataFrame({
    "a": ["the cat is blue", "the sky is green", "the dog is black"]
})

我想检查这些行中是否有包含某个单词的行，我必须这样做。

frame["b"] = (
   frame.a.str.contains("dog") |
   frame.a.str.contains("cat") |
   frame.a.str.contains("fish")
)

帧[“b”]输出：

0     True
1    False
2     True
Name: b, dtype: bool

如果我决定列一个清单：

mylist = ["dog", "cat", "fish"]

如何检查行是否包含列表中的某个单词？

Answer 1

在检查了提取字符串的已接受答案的注释之后，也可以尝试这种方法。

frame = pd.DataFrame({'a' : ['the cat is blue', 'the sky is green', 'the dog is black']})

frame
              a
0   the cat is blue
1  the sky is green
2  the dog is black

让我们创建我们的列表，其中包含需要匹配和提取的字符串。

mylist = ['dog', 'cat', 'fish']
pattern = '|'.join(mylist)

现在，让我们创建一个函数，该函数将负责查找和提取子字符串。

import re
def pattern_searcher(search_str:str, search_list:str):

    search_obj = re.search(search_list, search_str)
    if search_obj :
        return_str = search_str[search_obj.start(): search_obj.end()]
    else:
        return_str = 'NA'
    return return_str

我们会把这个功能用在熊猫身上。DataFrame.apply

frame['matched_str'] = frame['a'].apply(lambda x: pattern_searcher(search_str=x, search_list=pattern))

结果：

              a             matched_str
   0   the cat is blue         cat
   1  the sky is green         NA
   2  the dog is black         dog

Answer 2

因为这个清单应该有用

print(frame[frame["a"].isin(mylist)])

请参见pandas.DataFrame.isin（）。

Answer 3

frame = pd.DataFrame({'a' : ['the cat is blue', 'the sky is green', 'the dog is black']})

frame
                  a
0   the cat is blue
1  the sky is green
2  the dog is black

str.contains方法接受正则表达式模式：

mylist = ['dog', 'cat', 'fish']
pattern = '|'.join(mylist)

pattern
'dog|cat|fish'

frame.a.str.contains(pattern)
0     True
1    False
2     True
Name: a, dtype: bool

由于支持正则表达式模式，您还可以嵌入标志：

frame = pd.DataFrame({'a' : ['Cat Mr. Nibbles is blue', 'the sky is green', 'the dog is black']})

frame
                     a
0  Cat Mr. Nibbles is blue
1         the sky is green
2         the dog is black

pattern = '|'.join([f'(?i){animal}' for animal in mylist])  # python 3.6+

pattern
'(?i)dog|(?i)cat|(?i)fish'
 
frame.a.str.contains(pattern)
0     True  # Because of the (?i) flag, 'Cat' is also matched to 'cat'
1    False
2     True