Python 检查熊猫数据框列中的字符串是否在列表中

check if string in pandas dataframe column is in list

提问by user2333196

If I have a frame like this

如果我有这样的框架

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

and I want to check if any of those rows contain a certain word I just have to do this.

我想检查这些行中是否有任何一行包含某个单词，我只需要这样做。

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

frame['b']outputs:

frame['b']输出：

True
False
True

If I decide to make a list

如果我决定列一个清单

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

how would I check that the rows contain a certain word in the list?

我将如何检查行中是否包含列表中的某个单词？

采纳答案by Andy Hayden

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

The str.containsmethod accepts a regular expression pattern:

该str.contains方法接受一个正则表达式模式：

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

Because regex patterns are supported, you can also embed flags:

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

回答by Meloun

For list should work

对于列表应该工作

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

http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.isin.html

http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.isin.html

回答by Aman Raparia

After going through the comments of the accepted answer of extracting the string, this approach can also be tried.

在浏览了提取字符串的已接受答案的注释后，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

Let us create our list which will have strings that needs to be matched and extracted.

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)

Now let create a function which will be responsible to find and extract the substring.

现在让我们创建一个函数来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

We will use this function with pandas.DataFrame.apply

我们将这个函数与 pandas.DataFrame.apply 一起使用

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

Result :

结果 ：

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