Changing value in dataframe with the mean value based on condition

Question

I have a dictionary that contains the mean of the price of each product:

{"Apple": 4.50, "Orange": 5.00, 'Banana': 2.00}

What I would like to do is to apply these mean values to rows in my DataFrame that contain a non valid (<=0) value in the "Price" column.

ID	Product	Price
1	Apple	0
2	Orange	-1
1	Banana	-1
2	Apple	3.99

I tried to override/change the values by iterating (which I know isn't a good way to do this) and applying the mean value, but I am getting an error SettingWithCopyWarning:

for i in df[df["Price"]<=0].index:
# Row location based on index
  df.loc[i]["Price"] = mean_prices_dict[df.loc[i]["Product"]]

score 0 · Accepted Answer · answered Aug 25 '21 at 09:26

Use Series.map only for filtered rows:

d = {"Apple": 4.50, "Orange": 5.00, 'Banana': 2.00}

mask = df["Price"]<=0
df.loc[mask, 'Price'] = df.loc[mask, 'Product'].map(d)
print (df)
   ID Product  Price
0   1   Apple   4.50
1   2  Orange   5.00
2   1  Banana   2.00
3   2   Apple   3.99

Changing value in dataframe with the mean value based on condition

1 Answers1