使用 itterrows 向 Pandas df 添加行

Question

I have the following pandas datframe

For each country I wish to create as many rows as the number of years it exists. For instance, the US will have 201 rows, Canada 95 and so forth.

I thought of doing something like:

for row in df.iterrows():
    for range(row['styear'], row['endyear']):
        df.append(row)

Any ideas how to make this work?

Answer 1

You can create a new column with the range of years, and then explode that column

# sample dataframe
df = pd.DataFrame({
    'country': ['United States', 'Canada', 'Bahamas', 'Cuba'],
    'styear': [1816, 1920, 1973, 1902],
    'endyear': [2016, 2016, 2016, 1906]
})


df['allyears'] = [range(start, end+1)
    for start, end in zip(df.styear, df.endyear)]
df = df.explode('allyears')
print(df)

Output

          country  styear  endyear allyears
0   United States    1816     2016     1816
0   United States    1816     2016     1817
0   United States    1816     2016     1818
0   United States    1816     2016     1819
0   United States    1816     2016     1820
..            ...     ...      ...      ...
3            Cuba    1902     1906     1902
3            Cuba    1902     1906     1903
3            Cuba    1902     1906     1904
3            Cuba    1902     1906     1905
3            Cuba    1902     1906     1906

[347 rows x 4 columns]