Pandas - ValueError on datetime format mismatch

Question

This is my data:

date = df['Date']
print (date.head())

0   2015-01-02
1   2015-01-02
2   2015-01-02
3   2015-01-02
4   2015-01-02
Name: Date, dtype: datetime64[ns]

my code:

def date_to_days(date):
    return date2num(datetime.datetime.strptime(date, '%Y-%m-%d'))

Why am I getting that error?

Answer 1

It works fine for me without any errors.

In [74]: from matplotlib.dates import date2num

In [75]: df['Number of days'] = df['Date'].apply(lambda x: date2num(datetime.datetime.strptime(x, '%Y-%m-%d')))

In [76]: df
Out[76]: 
         Date  Number of days
0  2015-01-02        735600.0
1  2015-01-02        735600.0
2  2015-01-02        735600.0
3  2015-01-02        735600.0
4  2015-01-02        735600.0

In general, it's a bad practice to assign variables to a pandas series object. It can mess a lot of things up.

In [1]: def date_to_days(date):
   ...:     return date2num(datetime.datetime.strptime(date, '%Y-%m-%d'))

In [2]: df['Number of days'] = df['Date'].apply(date_to_days)

In [3]: df
Out[3]: 
         Date  Number of days
0  2015-01-02        735600.0
1  2015-01-02        735600.0
2  2015-01-02        735600.0
3  2015-01-02        735600.0
4  2015-01-02        735600.0