通过一次追加一行来创建 Pandas 数据框

2022-01-22 00:00:00 python pandas dataframe append

问题描述

我了解 Pandas 旨在加载完全填充的 DataFrame，但我需要创建一个空的 DataFrame，然后逐一添加行.最好的方法是什么?

I understand that Pandas is designed to load a fully populated DataFrame, but I need to create an empty DataFrame then add rows, one by one. What is the best way to do this?

我成功创建了一个空的DataFrame:

I successfully created an empty DataFrame with:

res = DataFrame(columns=('lib', 'qty1', 'qty2'))

然后我可以添加一个新行并用以下内容填充一个字段:

Then I can add a new row and fill a field with:

res = res.set_value(len(res), 'qty1', 10.0)

它可以工作，但看起来很奇怪:-/(添加字符串值失败.)

It works, but it seems very odd :-/ (It fails for adding a string value.)

如何向我的 DataFrame 添加新行(具有不同的列类型)?

How can I add a new row to my DataFrame (with a different columns type)?

解决方案

你可以使用df.loc[i]，其中索引为i的行会是什么您指定它在数据框中.

You can use df.loc[i], where the row with index i will be what you specify it to be in the dataframe.

>>> import pandas as pd
>>> from numpy.random import randint

>>> df = pd.DataFrame(columns=['lib', 'qty1', 'qty2'])
>>> for i in range(5):
>>>     df.loc[i] = ['name' + str(i)] + list(randint(10, size=2))

>>> df
     lib qty1 qty2
0  name0    3    3
1  name1    2    4
2  name2    2    8
3  name3    2    1
4  name4    9    6

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