CODEWITHSUNDEEP
pandas
Smith Dwayne
Smith Dwayne

Reputation: 2807

Update a column with another table column where another column of the table is equal with each other pandas

I have two pandas data frame as below,

Left_Frame 
       symbol    price timelab1 timelab2 timelab3     _merge
    0  145822  10.5018    19:00                    left_only
    1  145819  10.5055    19:00                    left_only
Right_Frame
        symbol  price timelab1 timelab2 timelab3      _merge
    16  145822  10.58      NaN      NaN      NaN  right_only
    17  145819  10.55      NaN      NaN      NaN  right_only

I want to update Left_Frame price with Right_Frame price where symbol are equal to the both data frames. Expected result is,

Left_Frame 
       symbol    price timelab1 timelab2 timelab3     _merge
    0  145822  10.58      19:00                    left_only
    1  145819  10.55      19:00                    left_only

How can I do this in Pandas?

Upvotes: 0

Views: 43

Answers (2)

iamklaus
iamklaus

Reputation: 3770

this would do the job

I want to update Left_Frame price with Right_Frame price where symbol are equal to the both data frames. Expected result is

left_frame['price'] = np.where(left_frame['symbol'].values == right_frame['symbol'].values, right_frame['price'],left_frame['price'])

Update

left_frame.loc[:,'price'] = np.where(left_frame['symbol'].values == right_frame['symbol'].values, right_frame['price'],left_frame['price'])

Upvotes: 2

jezrael
jezrael

Reputation: 862681

Use Series.map by another Series created by DataFrame.set_index and for unmatched values replace by original by Series.fillna:

print (Left_Frame)
   symbol  price timelab1  timelab2  timelab3     _merge
0  145822     12    19:00       NaN       NaN  left_only
1  100000     13    19:00       NaN       NaN  left_only


print (Right_Frame)
    symbol  price  timelab1  timelab2  timelab3      _merge
16  145822     10       NaN       NaN       NaN  right_only
17  145819     18       NaN       NaN       NaN  right_only

s = Right_Frame.set_index('symbol')['price']
Left_Frame['price'] = Left_Frame['symbol'].map(s).fillna(Left_Frame['price'])

#slowier alternative
#Left_Frame['price'] = Left_Frame['symbol'].replace(s)

print (Left_Frame)
   symbol  price timelab1  timelab2  timelab3     _merge
0  145822   10.0    19:00       NaN       NaN  left_only
1  100000   13.0    19:00       NaN       NaN  left_only

Upvotes: 1

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