why we can't use eval with str in here?

Question

Why this is achieved by repr method only?

import datetime
d=datetime.datetime.now()
x=str(d)
y=eval(x)
print(y)

It's showing

SyntaxError: invalid token

Did you look at the strings you're trying to evaluate? Only one is syntactically valid Python. — jonrsharpe, Jul 08 '19 at 06:54

score 0 · Accepted Answer · answered Jul 08 '19 at 06:50

0

When you call str(datetime.datetime.now()), you get a string representing the current time such as 2019-07-08 19:32:04.078030.

But when repr(datetime.datetime.now()) is called, the actual format of the datetime object is returned. Something like datetime.datetime(2019, 7, 08, 19, 32, 4, 78030).

eval() evaluates the string as a python function. since 2019-07-08 19:32:04.078030 is not a python command, you get an error. datetime.datetime(2019, 7, 08, 19, 32, 4, 78030) however is a python command and is executed.

Overall the programs that will work are

Using str():

import datetime
d=datetime.datetime.now()
x=str(d)
print(x)

Using repr():

import datetime
d=datetime.datetime.now()
x=repr(d)
y=eval(x)
print(y)

answered Jul 08 '19 at 06:50

Prateek Dhanuka

380
2
22

But my programs runs fine when I am not using eval, why so? – PRIYANSHU DUBEY Jul 08 '19 at 08:18
What do you mean? Do you mean there are no errors? – Prateek Dhanuka Jul 08 '19 at 08:20
yes, remove eval and there will be no error – PRIYANSHU DUBEY Jul 09 '19 at 04:34
Yes, removing eval will not result in an error but your output will now look something like `datetime.datetime(2019, 7, 08, 19, 32, 4, 78030)` instead of `2019-07-08 19:32:04.078030` – Prateek Dhanuka Jul 09 '19 at 04:44
Yes, got the solution. Thanks – PRIYANSHU DUBEY Jul 10 '19 at 05:45

why we can't use eval with str in here?

1 Answers1