Filter a pandas dataframe by a boolean function-CodePudding

I need to filter a pandas dataframe using a function on only one column of string.

Here an example of dataframe :

  ID  Titles    Values
0  1  title1   value1
1  2  title2   value2
2  3  title3   value3
...

I have a complex function :

def checkTitle(title:str) -> bool :
    ...

And I want to filter the first dataframe with this function on the column Titles, with only the rows where the function send True.

I try something like that but it doesn't return anything usable :

df = df.apply(checkTitle(df["Titles"]),axis=1)

Can you help please ?

CodePudding user response：

You can apply the function to just one column of the dataframe and then use the resulting Boolean series to select the rows:

select = df.Titles.apply(checkTitle)
df = df.loc[select, :]

CodePudding user response：

I think this might be a solution for you.

def checkTitle(title:str) -> bool:
    if title == 'title2':
        return True
    else:
        return False

df = pd.DataFrame({'ID': [1, 2, 3, 4], 'Titles': ['title1', 'title2', 'title2', 'title3'], 'Values': ['value1', 'value2', 'value2', 'value3']})

mask = df.Titles.apply(checkTitle)
df[mask]

I don't know your function in detail, but you need to return both bool values True|False to slice the dataframe.

I hope this solution helps

Regards,