Merging csv files with different headers with Pandas in Python

From your example, it looks like you need to do some column renaming in addition to the merge. This is easiest done before the merge itself.

# Read the csv files
dfA = pd.read_csv("a.csv")
dfB = pd.read_csv("b.csv")

# Rename the columns of b.csv that should match the ones in a.csv
dfB = dfB.rename(columns={'MEASUREMENT': 'HEIGHT', 'COUNTRY': 'LOCATION'})

# Merge on all common columns
df = pd.merge(dfA, dfB, on=list(set(dfA.columns) & set(dfB.columns)), how='outer')

# Only keep the columns that exists in a.csv
df = df[dfA.columns]

# Save to a new csv
df.to_csv("output.csv", index=False)

This should give you what you are after.