[Python Debug] SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame.
I Got a SettingWithCopyWarning when I ran the following code:
tmp=date[date['date'].isnull().values==True]
tmp['date']=tmp['text'].str.extract(regex2,re.VERBOSE)
The details of the Warning are :
/Users/monica/anaconda3/lib/python3.6/site-packages/ipykernel_launcher.py:23: SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead
Then I got the inspiration from
https://stackoverflow.com/questions/20625582/how-to-deal-with-settingwithcopywarning-in-pandas
The
SettingWithCopyWarning
was created to flag potentially confusing "chained" assignments such as the following, which don't always work as expected, particularly when the first selection returns a copy.df[df['A'] > 2]['B'] = new_val # new_val not set in df
The warning offers a suggestion to rewrite as follows:
df.loc[df['A'] > 2, 'B'] = new_val
Or you can safely disable this new warning with the following assignment.
pd.options.mode.chained_assignment = None # default='warn'
Since we copied the dataframe firstly, there are some other options.
You can set the
is_copy
flag toFalse
, which will effectively turn off the check, for that object:tmp.is_copy = False
Or explicitly copy then no further warning will happen.
In my case, the problem was solved by add .copy( ) method while defining tmp, i.e.,
tmp=date[date['date'].isnull().values==True].copy()
tmp['date']=tmp['text'].str.extract(regex2,re.VERBOSE)
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