ValueError: Columns must be same length as key: python replacing DF1's column with DF2

Question

I have two dataframes. One dataframe one first, dataframe two second.

I want to replace country value based on DF 2.

Code	Country	Column C	Column D
100	NULL	foo	mei
200	NULL	bar	tes
100	NULL	foo1	mei1
200	NULL	bar1	tes1
100	NULL	foo2	mei2
200	NULL	bar2	tes2

Code	Country
100	Canada
200	USA

Tried:

df1['Country'] = df2.replace(df1['Code'],df1['Country']

But this is throwing error: Columns must be same length as key

Code	Country	Column C	Column D
100	Canada	foo	mei
200	USA	bar	tes
100	Canada	foo1	mei1
200	USA	bar1	tes1
100	Canada	foo2	mei2
200	USA	bar2	tes2

Answer 1

I would not use the replace method but a join.

import pandas as pd

code = [100, 200, 100, 200]
df1 =  pd.DataFrame(code, columns=['code'])
df1["country"] = None

df1.head()

# return
code    country
100     None
200     None
100     None
200     None


code2 = [100, 200]
coutry2 = ["Canada", "USA"]
df2 = pd.DataFrame(list(zip(code2, coutry2)), columns=['code', 'country'])
df2.head()
# output
code    country
100     Canada
200     USA


resutls = pd.merge(df1, df2, on='code', how='left')
resutls.head()

# output
 code   country_x   country_y
100     None        Canada
200     None        USA
100     None        Canada
200     None        USA

results_clean = resutls[['code', 'country_y']]
results_clean.columns = ['code', 'country']
results_clean.head()

code    country
100     Canada
200     USA
100     Canada
200     USA