Python で辞書キーに複数の値を追加する方法

2010
2
2009
4
1989
8
2009
7

{
    2010: 2,
    2009: [4, 7],  # Appended value for the same key
    1989: 8
}

<code class="python">years_dict = {}  # Empty dictionary to store years and values

# Iterate through the list of years and values
for line in list:
    year = line[0]   # Extract the year from the line
    value = line[1]  # Extract the value for the year

    # Check if the year is already in the dictionary
    if year in years_dict:
        # If it is, append the new value to the existing list
        years_dict[year].append(value)
    else:
        # If it's a new year, create a new list and add the first value
        years_dict[year] = [value]</code>