Combine pandas DataFrame query() method with isin()

Question

So I want to use isin() method with df.query(), to select rows with id in a list: id_list. Similar question was asked bef

Answer 1

From the docs for query

You can refer to variables in the environment by prefixing them with an '@' character like @a + b.

In your case:

In [38]: df.query('a == @id_list')
Out[38]:
   a  b  c  d
0  a  a  3  4
1  a  a  4  5
2  b  a  2  3
3  b  a  1  5
4  c  b  2  4
5  c  b  1  2

Answer 2

This appears to work:

>>> df.query('a == {0}'.format(id_list))
   a  b  c  d
0  a  a  4  1
1  a  a  0  7
2  b  a  2  1
3  b  a  0  1
4  c  b  4  0
5  c  b  4  2

Whether or not it is more clear is a matter of personal taste.

Answer 3

You can also include the list within the query string:

>>> df.query('a in ["a", "b", "c"]')

This is the same as:

>>> df.query('a in @id_list')