How to Append Multiple Values to a Single Key in a Python Dictionary?

Appending Multiple Values for One Key in a Dictionary

To create a dictionary with years as keys and associated values as lists in Python, one can approach the task as follows:

<code class="python">years_dict = dict()

for line in list:
    if line[0] in years_dict:
        years_dict[line[0]].append(line[1])
    else:
        years_dict[line[0]] = [line[1]]</code>

The given example, where the input years and associated values are:

2010
2
2009
4
1989
8
2009
7

would produce the following dictionary:

{
    "2010": [2],
    "2009": [4, 7],
    "1989": [8]
}

This approach ensures that each year key in the dictionary has an associated list of values, including any duplicates.

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