Pandaic way to check whether a dataframe has any rows

Question

Given a dataframe df, I'd apply some condition df[condition] and retrieve a subset. I just want to check if there are any rows in the subset - this would tell me the condition is a valid one.

In [551]: df
Out[551]: 
   Col1
0     1
1     2
2     3
3     4
4     5
5     3
6     1
7     2
8     3

What I want to check is something like this:

if df[condition] has rows:
    do something

What is the best way to check whether a filtered dataframe has rows? Here's some methods that don't work:

1. if df[df.Col1 == 1]: Gives ValueError: The truth value of a DataFrame is ambiguous.

2. if df[df.Col1 == 1].any(): Also gives ValueError

I suppose I can test the len. Are there other ways?

Answer 1

You could use df.empty:

df_conditional = df.loc[df['column_name'] == some_value]
if not df_conditional.empty:
    ... # process dataframe results