Pandas：如何根据 id 列表增加列的单元格值
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Pandas: how to increment a column's cell value based on a list of ids
提问by AlanH
I have a list of ids that correspond to the row of a data frame. From that list of ids, I want to increment a value of another column that intersects with that id's row.
我有一个对应于数据框行的 id 列表。从该 id 列表中，我想增加与该 id 行相交的另一列的值。
What I was thinking was something like this:
我的想法是这样的：
ids = [1,2,3,4]
for id in ids:
my_df.loc[my_df['id']] == id]['other_column'] += 1
But this doesn't work. How can I mutate the original df, my_df?
但这不起作用。我怎样才能改变原来的 df, my_df？
回答by MaxU
try this:
尝试这个：
my_df.loc[my_df['id'].isin(ids), 'other_column'] += 1
Demo:
演示：
In [233]: ids=[0,2]
In [234]: df = pd.DataFrame(np.random.randint(0,3, (5, 3)), columns=list('abc'))
In [235]: df
Out[235]:
a b c
0 2 2 1
1 1 0 2
2 2 2 0
3 0 2 1
4 0 1 2
In [236]: df.loc[df.a.isin(ids), 'c'] += 100
In [237]: df
Out[237]:
a b c
0 2 2 101
1 1 0 2
2 2 2 100
3 0 2 101
4 0 1 102
回答by NickBraunagel
the ids are unique, correct? If so, you can directly place the idinto the df:
id 是唯一的，对吗？如果是这样，您可以直接将id放入df：
ids = [1,2,3,4]
for id in ids:
df.loc[id,'column_name'] = id+1
