Converting String to datetime Python

Question

How would I convert the string 2014年05月19日 to a datetime object in Python if I'm reading it from a csv file? Currently when I specify dtype=None, it reads in 2014年05月19日 as a string, not a datetime.

import numpy as np
import datetime
np.genfromtxt(inputFile, dtype=None,delimiter=' ')

File

2014年05月19日 10
2014年05月20日 11
2014年05月21日 12
2014年05月22日 13.29
2014年05月23日 12.1

where the number after the string is a value associated with the date but not included in the datetime object

dataPoints = np.loadtxt(inputFile, dtype=None,delimiter=' ', converters = {0: datetime.datetime.strptime('%Y-%m-%d')})

I receive the following message: TypeError: strptime() takes exactly 2 arguments (1 given)

how do I specify the format without actually stripping the string?

• Lily Mara: what is the number after the space?
• MikeRixWolfe: Why do you have to use numpy? why not open the csv, split by comma, and strptime?

Answer 1

If you don't have missing values you can use numpy.loadtxt().

numpy.genfromtxt() also has the converters param. (thx RickyA)

Using 'coverters' param and lambda function:

from datetime import datetime
datestr2num = lambda x: datetime.strptime(x, '%Y-%m-%d')
np.genfromtxt(inputFile, delimiter=' ', converters = {0: datestr2num})

Where 0 is column index.

There is simpler way - use dtype param:

np.genfromtxt(inputFile, dtype=['datetime64[D]', float], delimiter=' ')

or more human readable using ('column name', type) tuple:

np.genfromtxt(inputFile, dtype=[('Date', 'datetime64[D]'),('Value', float)], delimiter=' ')

BTW IMHO Load string as datetime in numpy would be more accurate title.

• Apollo: but will this try to convert my associated value to a date as well?
• Piotr Nawrot: I just edited. You indicate which column will be converted by index. So the answer is no :-)
• RickyA: BTW. genfromtxt also has the converters param
• Apollo: @PiotrNawrot also, would datestr2num = '%Y-%m-%d' suffice?
• Apollo: @PiotrNawrot I'm still just a little confused by the datestr2num part, thanks.

Answer 2

You should use the strptime function from the datetime module. I'm not sure what the numbers after the space should be, but this will format the year-month-day correctly into a datetime object.

from datetime import datetime
some_date = '2014-05-28'
parsed_date = datetime.strptime(some_date, '%Y-%m-%d')
print(parsed_date)