Pandas replace DataFrame values [duplicate]

Question

I am trying to replace the values of a column in a df based on the corresponding index value pair in another df.

For example:

main df:

d = {'var1': [A, B, A, B]}
df = pd.DataFrame(data=d)
df
    var1   
0     A     
1     B     
2     A     
3     B

Data frame with new values:

df2  val1

A     1     
B     2

Result:

I was thinking I could set var1 as a temporary index then join with df2 and then replace the var1 column with val1. Not sure if there is a better way to do this?

Use map : df['var1'].map(df2['val1'])

Chris Adams
– Chris Adams

2019-03-25 16:12:01 +00:00
Commented Mar 25, 2019 at 16:12 — Chris Adams
– Chris Adams, Commented Mar 25, 2019 at 16:12

anky · Accepted Answer · 2019-03-25 16:12:43Z

3

Use df.set_index() and series.map():

df.var1=df.var1.map(df_new.set_index('df2')['val1'])
print(df)

   var1
0     1
1     2
2     1
3     2

answered Mar 25, 2019 at 16:12

anky

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2 Comments

BENY Over a year ago

Maybe try something new df2.val1.get(df.var1)

anky Over a year ago

@Wen-Ben Thank you. :) I will study more on get() thanks for teaching me that. :)

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