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I am trying to label a data frame by on-peak, mid-peak, off-peak etc. I managed to get the values I want to assign in this 'Mid-Peak', df['Peak'][df['func'] == 'Winter_Weekend']. However, when I include the .between_time I get the error: SyntaxError: can't assign to function call. I am not sure how to fix this. My goal is for the code code to work like this. Do I need another function or a do I need to change the syntax? Thank you for the help.

df['Peak'][df['func'] == 'Winter_Weekend'].between_time('16:00','21:00', include_end=False) = 'Mid-Peak'
Luis Enriquez-Contreras
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2 Answers2

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In general, you can't assign a result to a function call, so need a different syntax. You could try

selection = df[df['func'] == 'Winter_Weekend'].between_time('16:00','21:00', include_end=False)
selection["Peak"] = "Mid-Peak"

But this doesn't update your original df, only the rows copied into selection.

To update the original dataframe, one way is to use loc to select both rows and a column, and .index to apply the between_time selection to the original dataframe:

ww = df["func"] == "Winter_Weekend"
df.loc[df[ww].between_time('16:00', '21:00', include_end=False).index, "Peak"] = "Mid-Peak"
Stuart
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I would recommend leveraging np.where() here, as follows:

df['Peak'] = np.where(df[df['func'] == 'Winter_Weekend'].between_time('16:00','21:00', include_end=False), 'Mid-Peak', df['Peak'])
rahlf23
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