如何去除Series中的空列表，同时将非空列表变为字符串形式？

Question

The following is an example

df=pd.DataFrame({'AAA','BBBB','CCC'},columns=['fruit'])
a=pd.Series({'0':'A','1':'B','2':'C'})
dict_a={}
for x in a:
dict_a[x]=''.join('%s' %a for a in filter(None,df['fruit'].str.findall(r'.*{}.*'.format(x))))

The dictionary values I get are in list form：['AAA'],['BBB'] but my ideal form is：'AAA','BBB' How to remove the empty list in the Series, and at the same time change the non-empty list into a string form,I want to use it as the value of the dictionary?

Answer 1

To get only the 1st element of the match, take the list item at index 0:

for x in a:
    dict_a[x] = ''.join(m[0] for m in filter(None, df['fruit'].str.findall(r'.*{}.*'.format(x))))

# `dict_a` is:
{'A': 'AAA', 'B': 'BBBB', 'C': 'CCC'}

This will take only the first result of findall which might not give the results you want if you have more than one match in the dataframe or more than one match per row in the dataframe.

(Also, don't reuse the series name a in your loop. I've change it to m .)