How to apply a self defined function in Pandas

[Shaozhong SHI]

On Sun, 31 Oct 2021 at 19:28, MRAB <python at mrabarnett.plus.com> wrote:

> On 2021-10-31 18:48, Shaozhong SHI wrote:
> >
> > On Sunday, 31 October 2021, MRAB <python at mrabarnett.plus.com> wrote:
> >
> >     On 2021-10-31 17:25, Shaozhong SHI wrote:
> >
> >         I defined a function and apply it to a column in Pandas.  But
> >         it does not
> >         return correct values.
> >
> >         I am trying to test which url in a column full of url to see
> >         which one can
> >         be connected to or not
> >
> >         def connect(url):
> >              try:
> >                  urllib.request.urlopen(url)
> >                  return True
> >              except:
> >                  return False
> >
> >         df['URL'] = df.apply(lambda x: connect(df['URL']), axis=1)
> >
> >         I ran without any error, but did not return any true.
> >
> >         I just could not find any error with it.
> >
> >         Can anyone try and find out why
> >
> >     You're passing a function to '.apply'. That has one argument,' x'.
> >
> >     But what is the function doing with that argument?
> >
> >     Nothing.
> >
> >     The function is just returning the result of connect(df['URL']).
> >
> >     df['URL'] is a column, so you're passing a column to '.urlopen',
> >     which, of course, it doesn't understand.
> >
> >     So 'connect' returns False.
> >
> >
> > Please expand on how.
> >
> It's as simple as passing 'connect' to '.apply' as  the first argument.
>


Well, can you expand the the simplicity?

Regards, David

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