Create a parse function for different date formats in Python

I want to create a parse function with lambda able to recognize two different formats

"2014-01-06 15:23:00"

and

"2014-01-06"

The idea is to use this function to create a pandas dataframe but in some of the values the hour is missing

This is my first idea

parse = lambda x: pd.datetime.strptime(x, '%Y-%m-%d %H:%M:%S') if x is True else pd.datetime.strptime(x, '%Y-%m-%d')

it seems that x is True is not correct

Any idea??