Updating values with another dataframe

Question

I have 2 pandas dataframes. The second one is contained in the first one. How can I replace the values in the first one with the ones in the second?

consider this example:

df1 = pd.DataFrame(0, index=[1,2,3], columns=['a','b','c'])
df2 = pd.DataFrame(1, index=[1, 2], columns=['a', 'c'])

ris= [[1, 0, 1],
      [1, 0, 1],
      [0, 0, 0]]

and ris has the same index and columns of d1

A possible solution is:

for i in df2.index:
  for j in df2.columns:
     df1.loc[i, j] = df2.loc[i, j]

But this is ugly

jezrael · Accepted Answer · 2016-04-12 10:18:23Z

1

I think you can use copy with combine_first:

df3 = df1.copy()
df1[df2.columns] = df2[df2.columns]
print df1.combine_first(df3) 
     a  b    c
1  1.0  0  1.0
2  1.0  0  1.0
3  0.0  0  0.0

Next solution is creating empty new DataFrame df4 with index and columns from df1 and fill it by double combine_first:

df4 = pd.DataFrame(index=df1.index, columns=df1.columns)
df4 = df4.combine_first(df2).combine_first(df1)
print df4
     a    b    c
1  1.0  0.0  1.0
2  1.0  0.0  1.0
3  0.0  0.0  0.0

edited Apr 12, 2016 at 10:18

answered Apr 12, 2016 at 10:11

jezrael

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Comments

Abbas · Accepted Answer · 2016-04-12 10:08:39Z

0

Try

In [7]: df1['a'] = df2['a']

In [8]: df1['c'] = df2['c']

In [14]: df1[['a','c']] = df2[['a','c']]

If the column names are not known:

In [25]: for col in df2.columns:
   ....:     df1[col] = df2[col]

edited Apr 12, 2016 at 10:08

answered Apr 12, 2016 at 10:05

Abbas

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