检查数据框是否有任何行的 pandas 式方法 [英] Pandaic way to check whether a dataframe has any rows

问题描述

给出一个数据框df，我将应用一些条件df[condition]并检索一个子集.我只想检查子集中是否有任何行-这可以告诉我条件是有效的.

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

我要检查的是这样的:

if df[condition] has rows:
    do something

检查已过滤的数据框是否具有行的最佳方法是什么?这是一些无效的方法:

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]:给出ValueError: The truth value of a DataFrame is ambiguous.

if df[df.Col1 == 1].any():还给出了ValueError

我想我可以测试len.还有其他方法吗?

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

推荐答案

您可以使用df.empty:

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

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