stack_example.py

import pandas as pd

df = pd.DataFrame({
    'fruits': [['apple', 'banana'], ['orange', 'pear'], ['grape', 'kiwi', 'peach']]
})

# stack the dataframe
df = df['fruits'].apply(pd.Series).stack().reset_index(level=1, drop=True).to_frame('fruit')
df.index.name = 'id'
df = df.reset_index()

print(df)