how to filter dataframe based on a column value

Question

can someone tell me why filtering a dataframe based on a column value does not apply the filter, instead it fills the other columns with nan values, as the following pictures show

enter image description here

Please do not link or embed external images of source code or data. Images make it difficult to efficiently assist you as they cannot be copied and offer poor usability as they cannot be searched. See: [Why not upload images of code/errors when asking a question?](https://meta.stackoverflow.com/q/285551/15497888) If you need assistance formatting a small sample of your DataFrame as a copyable piece of code for SO see [How to make good reproducible pandas examples](https://stackoverflow.com/q/20109391/15497888). — Henry Ecker, Dec 23 '21 at 23:15

score 0 · Answer 1 · answered Dec 23 '21 at 23:33

To test a column for NaN, use isna(). See example below. Hope this is helpful, please leave a comment if something doesn't work

import pandas as pd
df = pd.DataFrame(data={"col1": [1,2], "col2": ["three",float('nan')]})
df[df.col2.isna()]

Output

	col1	col2
1	2	nan

score 0 · Answer 2 · answered Dec 23 '21 at 23:52

Please don't link images to external sources, and use code blocks. Easily accessible data in questions is critical to reproducing the problem.

import numpy as np
import pandas as pd

dates = pd.date_range("20211223", periods=6)
df = pd.DataFrame(np.random.randn(6, 4), index=dates, columns=list("ABCD"))

print(f"{df[df['A'] > 1]}")

You were mostly on the right track. Instead on df[df['TYPE' == 'RNA']] you should use df[df['TYPE'] == 'RNA']

how to filter dataframe based on a column value

2 Answers2