How to apply a self defined function in Pandas
MRAB
python at mrabarnett.plus.com
Sun Oct 31 14:08:51 EDT 2021
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.
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