Query local variables passed in loop using pandas query function

Question

I want to be able to query each column name dynamically given the column names in a list. I can use the @sign to pass in dynamically on the other side of the equal sign but I'm really trying to do the columns dynamically..

import pandas as pd
import bumpy as np

df = pd.DataFrame(np.random.randn(10, 2), columns=list('ab'))
df

columns = ['a','b']

for each_column in columns:
    df.query("@each_column > 1")  ## error

even if we provided you with a string to query with, it's unclear what you're after. Your code won't produce any output. What is your desired result? — piRSquared
– piRSquared, Commented Jun 15, 2017 at 20:00

MaxU - stand with Ukraine · Accepted Answer · 2017-06-15 20:09:55Z

1

IIUC:

In [12]: df
Out[12]:
          a         b
0 -0.272252 -0.467849
1 -0.221294 -2.583866
2 -0.117282  1.044487
3  0.451677 -0.434122
4  0.899038  0.712295
5  1.591961  0.031358
6 -1.398513 -0.600160
7  1.073948  1.348097
8 -1.016790 -0.773364
9 -0.628775  1.116282

dynamically generating a query:

In [13]: q = ' and '.join('{} > 1'.format(c) for c in df.columns)

In [14]: q
Out[14]: 'a > 1 and b > 1'

In [15]: df.query(q)
Out[15]:
          a         b
7  1.073948  1.348097

edited Jun 15, 2017 at 20:09

answered Jun 15, 2017 at 20:02

MaxU - stand with Ukraine

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1 Comment

runningbirds Over a year ago

not exactly how I was seeing things, but this gives me what I need to solve this. thanks

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