Count appearances of a string throughout columns in pandas

问题

Consider the following dataframe:

import pandas as pd
df = pd.DataFrame(["What is the answer", 
                   "the answer isn't here, but the answer is 42" , 
                   "dogs are nice", 
                   "How are you"], columns=['words'])
df
                                         words
0                           What is the answer
1  the answer isn't here, but the answer is 42
2                                dogs are nice
3                                  How are you

I want to count the number of appearances of a certain string, that may repeat a few times in each index.

For example, I want to count the number of times the answer appears. I tried:

df.words.str.contains(r'the answer').count()

Which I hoped for a solution, but the output is 4. Which I don't understand why. the answer appears 3 times.

What is **the answer**
**the answer** isn't here, but **the answer** is 42

Note: search string may appear more than once in the row

回答1:

You need str.count

In [5285]: df.words.str.count("the answer").sum()
Out[5285]: 3

In [5286]: df.words.str.count("the answer")
Out[5286]:
0    1
1    2
2    0
3    0
Name: words, dtype: int64

来源：https://stackoverflow.com/questions/46893629/count-appearances-of-a-string-throughout-columns-in-pandas