擅长:python、mysql、java
<pre><code>import pandas as pd
import numpy as np
# Just Creating your dataframes
raw_data = pd.DataFrame([('ABC', 2.6), ('ABB', np.nan), ('ACC', np.nan)], columns=['Country_code', 'homicides_per_100k'] )
homi_set = pd.DataFrame([('ABC', 2.6), ('ACC', 11), ('ABB', 3.1), ('ADD', 0.5)], columns=['Country_code', 'year'] )
# Left Join
new_set = pd.merge(raw_data, homi_set, on='Country_code', how='left')
# condition on the column
new_set['homicides_per_100k'] = np.where(new_set['homicides_per_100k'].isnull(), new_set['year'], new_set['homicides_per_100k'] )
del new_set['year']
new_set
</code></pre>
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