将字符串函数应用于pandas数据框列

Question

this seems somewhat basic but after going through stackoverflow I couldn't seem to take everything answered and solve my problem. so i'm working on my text processing skills. I put car reviews in a pandas dataframe looking like this:

    Review
0   :P I like you, Merc. You make me laugh! If Mat...
1   I am surprised that I did not find any discuss...
3   . . .let me see if I am following along correc...
4   . . .now hold on a minute. A "current" A6 4.2 ...
5   but has anyone noticed the front oh the new ac...

i wrote a function that takes a string as input and returns a value (in my case a sentiment score). within my function, this value will be put in a newly created column. the problem I obviously keep coming across is with the input - i get an expected string error. with a dataframe, there are objects not strings.

the function is very long and works when a string is inputed. here's a snippet of the function: note that dataframe is titled edmunds.

def checker(b):
    word = 'ls'
    if stry.find(word) == -1:
        edmunds['ls'] = 0.0
    ...
    edmunds['ls'] = sum(o_list)

any help would be greatly appreciated. trying to wrap my head around if i should go from dataframe to list or if i could still work within pandas.

output would ideally look like:

Review                                                 ls
0   :P I like you, Merc. You make me laugh! If Mat...  0.4
1   I am surprised that I did not find any discuss...  0.5
3   . . .let me see if I am following along correc...  0.0
4   . . .now hold on a minute. A "current" A6 4.2 ...  1.0
5   but has anyone noticed the front oh the new ac...  -0.6

Answer 1

To create a column ls from the column Review :

1. You need a function that takes one string and returns one number. Currently, the checker function doesn't do that, since it doesn't return anything (and also sets values inside edmunds , which is not necessary). Given how the function looks, you will probably want to end the function with a return sum(o_list) . And, to be clear, the input b must be a single string. One way to test this: you should be able to write checker("hello") and get a number back.

2. If you've written checker that way, then you can create ls easily: edmunds['ls'] = edmunds.Review.apply(checker)

In case you want to get more background on why Pandas works this way: The apply function is an example of mapping (a function over a list).