woodhead92 woodhead92 - 1 month ago 8
Python Question

Python - Access column based on another column value

I have the following dataframe in python

+-------+--------+
| Value | Number |
+-------+--------+
| true | 123 |
| false | 234 |
| true | 345 |
| true | 456 |
| false | 567 |
| false | 678 |
| false | 789 |
+-------+--------+


How do I conduct an operation which returns a list of all the 'Number' which has Value == TRUE

The output list expected from the above table is

['123', '345', '456']


Thanks in advance!

Answer

df.loc[df['Value'],'Number'] should work assuming the dtype for 'Value' are real booleans:

In [68]:
df.loc[df['Value'],'Number']

Out[68]:
0    123
2    345
3    456
Name: Number, dtype: int64

The above uses boolean indexing, here the boolean values are a mask against the df.

If you want a list:

In [69]:
df.loc[df['Value'],'Number'].tolist()

Out[69]:
[123, 345, 456]