Pandas Operate on Multiple Rows with Boolean Operator

pandas_multirow_apply.py

import pandas as pd

def r(row):
  if row['lat'] < 5:
    return row['data']
  elif row['lat'] >= 5:
    return 10 * row['data']

df = pd.DataFrame({ 'data': range(10), 'lat': range(10)}, columns=["lat", "data"])

print(df)

df['adj'] = df.apply(r, axis=1)

print(df)

How about:

df['adj'] = df['data']
rows_to_scale = df['lat'] >= 5
df.loc[rows_to_scale, 'adj'] *= 10.