pandas 如何将带有列表值的熊猫列连接到一个列表中？
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How to concatenate pandas column with list values into one list?
提问by SarwatFatimaM
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
我有一个数据框，其中一列在每个索引处都有一个列表。我想将这些列表连接成一个列表。我在用
ids = df.loc[0:index, 'User IDs'].values.tolist()
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'......]'].
然而，这导致
['[1,2,3,4......]']which 是一个字符串。不知何故，我的列表列中的每个值都是 type str。我曾尝试使用 转换list()，literal_eval()但它不起作用。该list()列表中的每个元素从转换成字符串如[12,13,14...]来['['1'',','2',','1',',','3'......]']。
How to concatenate pandas column with list values into one list? Kindly help out, I am banging my head on it for several hours.
如何将带有列表值的Pandas列连接到一个列表中？请帮忙，我正在敲打它几个小时。
回答by piRSquared
consider the dataframe df
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]
pandassimplest answer
pandas最简单的答案
df.col1.sum()
[1, 2, 3, 1, 2, 3]
numpy.concatenate
numpy.concatenate
np.concatenate(df.col1)
array([1, 2, 3, 1, 2, 3])
chain
chain
from itertools import chain
list(chain(*df.col1))
[1, 2, 3, 1, 2, 3]
response to comments:
I think your columns are strings
回复评论：
我认为你的列是字符串
from ast import literal_eval
df.col1 = df.col1.apply(literal_eval)
If instead your column is string values that look like lists
如果您的列是看起来像列表的字符串值
df = pd.DataFrame(dict(col1=['[1, 2, 3]'] * 2))
print(df) # will look the same
col1
0 [1, 2, 3]
1 [1, 2, 3]
However pd.Series.sumdoes not work the same.
但是pd.Series.sum不一样。
df.col1.sum()
'[1, 2, 3][1, 2, 3]'
We need to evaluate the strings as if they are literals and then sum
我们需要评估字符串，就好像它们是文字一样，然后 sum
df.col1.apply(literal_eval).sum()
[1, 2, 3, 1, 2, 3]
回答by zipa
If you want to flatten the list this is pythonicway to do it:
如果您想展平列表，可以pythonic这样做：
import pandas as pd
将Pandas导入为 pd
df = pd.DataFrame({'A': [[1,2,3], [4,5,6]]})
a = df['A'].tolist()
a = [i for j in a for i in j]
print a
