python - pandas DataFrame 不合并但不报错

Question

我有一个简单的循环，将句子编号和数字 + 1 相加，并将其创建到一个具有命名列 one 和 two 的 DataFrame 中。我试图将每次迭代的结果合并到主 DataFrame df 中，但它似乎没有合并它，也没有抛出错误。

这是可重现的代码:

df = pd.DataFrame()
for i in range(1, 6):
    sentence = pd.DataFrame((f'This is sentence {i}', i+1)).transpose()
    sentence.columns = ['one', 'two']
    print(sentence)
    if df.empty:
        df = sentence
        print('creating')
    else:
        df = df.merge(sentence, how='left', on=['one', 'two'])
        print('merging')

但是 df 的最终结果看起来只有一行:

                  one two
0  This is sentence 1   2

有人可以向我解释为什么这没有合并吗？

谢谢

编辑

最终结果应该是这样的:

                  one two
0  This is sentence 1   2
1  This is sentence 2   3
2  This is sentence 3   4
3  This is sentence 4   5
4  This is sentence 5   6

与合并时索引均为0有关吗？

Answer 1

for i in range(1, 6):
    sentence = pd.DataFrame([(f'This is sentence {i}', i+1)], columns=['one', 'two'])
    df = df.merge(sentence, how='outer')```

>>> df
                  one  two
0  This is sentence 1    2
1  This is sentence 2    3
2  This is sentence 3    4
3  This is sentence 4    5
4  This is sentence 5    6