Python String to dateTime conversion

Question

I have a string like

a = "datetime.datetime(2009,04,01)"

I would like to convert this to a datetime object in python. How should I proceed?

• aghast: How many other types of strings are there? Is datetime.datetime the only one, or do other class names appear?
• plasmon360: import datetime and then date = eval(a)

Answer 1

The code in the previous answer would work, but using eval is considered risky, because an unexpected input could have disastrous consequences. (Here's more info on why eval can be dangerous.)

A better option here is to use Python's strptime method:

from datetime import datetime
datetime_string = "datetime.datetime(2017, 3, 31)"
format = "datetime.datetime(%Y, %m, %d)"
datetime_object = datetime.strptime(datetime_string, format)

There are lots of different formats you can use for parsing datetimes from strings. You may want to check out the docs: https://docs.python.org/2/library/datetime.html#strftime-strptime-behavior

• Carolyn Conway: I prefer this code over eval also because it's clear about exactly what it's trying to do. With eval, you would have to read the surrounding code to understand what's happening, which can make debugging hard later on.
• s.dutta: Thanks a lot. That fixed it!!

Answer 2

You can use eval

eval('datetime.datetime(2009, 1, 1)')

You'll have to make sure datetime is imported first

>>> import datetime
>>> d = datetime.datetime(2009, 1, 1)
>>> repr(d)
'datetime.datetime(2009, 1, 1, 0, 0)`
>>> eval(repr(d))
datetime.datetime(2009, 1, 1, 0, 0)

• Patrick Haugh: Worth noting: nedbatchelder.com/blog/201206/eval_really_is_dangerous.html
• Brendan Abel: @PatrickHaugh Well, running any untrusted code is dangerous, with or without eval. It's just that historically eval-type functionality has been used to run arbitrary statements from users. There really just aren't many use cases for eval. If you're using it, there's probably a much better and safer way to do what you want to accomplish without eval.
• Eric Duminil: Nope. With datetime.strptime, the worst that can happen is that you get a wrong month/day. With eval, you could lose control of your server.

Answer 3

you could use eval. eval lets run python code within python program

a = "datetime.datetime(2009,04,01)" 
import datetime
a = eval(a)
print a
print type(a)

will result in

2009年04月01日 00:00:00
<type 'datetime.datetime'>