如何将具有列表值的pandas列连接到一个列表中? [英] How to concatenate pandas column with list values into one list?

问题描述

我有一个数据框，它的列之一在每个索引处都有一个列表.我想将这些列表合并为一个列表.我正在使用

I have a dataframe with one of its column having a list at each index. I want to concatenate these lists into one list. I am using

ids = df.loc[0:index, 'User IDs'].values.tolist()

但是，这导致 ['[1,2,3,4......]']这是一个字符串.不知何故，我的列表列中的每个值都是str类型.我尝试使用list()，literal_eval()进行转换，但是它不起作用. list()将列表中的每个元素转换为字符串，例如从[12,13,14...]到['['1'',','2',','1',',','3'......]'].

However, this results in ['[1,2,3,4......]'] which is a string. Somehow each value in my list column is type str. I have tried converting using list(), literal_eval() but it does not work. The list() converts each element within a list into a string e.g. from [12,13,14...] to ['['1'',','2',','1',',','3'......]'].

如何将具有列表值的pandas列连接到一个列表中?请帮忙，我在上面敲了几个小时.

How to concatenate pandas column with list values into one list? Kindly help out, I am banging my head on it for several hours.

推荐答案

考虑数据框df

df = pd.DataFrame(dict(col1=[[1, 2, 3]] * 2))
print(df)

        col1
0  [1, 2, 3]
1  [1, 2, 3]

pandas最简单的答案

pandas simplest answer

df.col1.sum()

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

numpy.concatenate

np.concatenate(df.col1)

array([1, 2, 3, 1, 2, 3])

chain

from itertools import chain

list(chain(*df.col1))

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

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回复评论:
我认为您的专栏是字符串

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response to comments:
I think your columns are strings

from ast import literal_eval

df.col1 = df.col1.apply(literal_eval)

如果相反，您的列是看起来像列表的字符串值

If instead your column is string values that look like lists

df = pd.DataFrame(dict(col1=['[1, 2, 3]'] * 2))
print(df)  # will look the same

        col1
0  [1, 2, 3]
1  [1, 2, 3]

但是pd.Series.sum不能正常工作.

df.col1.sum()

'[1, 2, 3][1, 2, 3]'

我们需要像对待文字一样评估字符串，然后sum

We need to evaluate the strings as if they are literals and then sum

df.col1.apply(literal_eval).sum()

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

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