数据：

使用merge_column()函数即可：

import pandas as pd


def merge_column(dataframe, column, seq=';') -> set:
    merge_sentence = set()
    all_sentences = dataframe[column].values.tolist()
    for s in all_sentences:
        if not pd.isna(s):
            for i in s.split(seq):
                merge_sentence.add(i)
    return merge_sentence


if __name__ == '__main__':
    df: pd.DataFrame = pd.DataFrame([
        ['a;b', 4.2],
        ['b;c', 0.03],
        ['a', 0]
    ], columns=['one', 'two'])
    print(merge_column(df, column='one', seq=';'))