python dataframe如何根据索引条件删除一些行

Question

To say I had a daily price dataframe with the date as its index. and I'd like to delete all the rows if its index date <"2010/1/1" . I tried bars.drop(bars.index<'2010/7/17'== True) It raised an error ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() . Any ideas?

Answer 1

If you actually wants to drop rows with your condition you could do following:

bars.drop(bars.index[bars.index<'2010/1/1'])

But it's better to slice dataframe using @EdChum solution with loc .