How to convert list column to a non-nested list?

Question

How to convert a column to a non-nested list while the column elements are list?

For example, the column is like

column
[1, 2, 3]
[1, 2]

<

Answer 1

We concatenate lists with the + operator. Because a pandas series uses its' elements underlying + operation when you call pd.Series.sum, we can concatenate a whole column, or series, of lists with.

df.column.sum()

[1, 2, 3, 1, 2]

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But if you're looking for performance, you can consider cytoolz.concat

import cytoolz

list(cytoolz.concat(df.column.values.tolist()))

[1, 2, 3, 1, 2]