[Tutor] Problems with pytz module

[Peter Otten]

Daniel Bosah wrote:

> I'm learning about OOP programming in Python.
> This is my code from my online course.
> 
> import datetime
> import pytz
> class Account:
>     """""""Simple account class with balance"""""""

Why so many "s ? Use either one for single-line strings

"Simple account class with balance."

or three for multiline strings

"""Simple account class with balance.
   yadda yadda...
"""


>     def __init__(self,name,balance):
>         self.name = name
>         self.balance = balance
>         self.transaction_list = []
>         print "Account created for " + self.name
> 
>     def deposit(self,amount):
>         if amount > 0:
>             self.balance += amount
>             self.show_balance()
> 
> 
self.transaction_list.append((pytz.utc.localize(datetime.datetime.utcnow()),amount))
> # appends traction details to list

That's either an indentation error in your code or a cut-and-past mishap.

>     def withdrawl(self,amount):
>          if 0 < amount <= self.balance:
>                 self.balance -= amount
>          else:
>             print "The account must be greater then zero and no more then
> your account balance"
>          self.show_balance()

Looks like you don't add anything to the transaction_list for withdrawals.

>     def show_balance(self):
>         print "Balance is {}".format(self.balance)
> 
>     def show_transactions(self):
>         for date, amount in self.transaction_list:
>             if amount > 0:
>                 tran_type = "deposited"
>             else:
>                 tran_type = "withdrawn"
>                 amount *= -1 # to show negative number
>                 print "{:6} {} on {} (local time was {})".format(amount,
> tran_type, date, date.astimezone())

Do you want to print only when money is withdrawn?

> 
> if __name__ == '__main__':
>     tim = Account("Tim", 0)
>     tim.show_balance()
> 
> 
>     tim.deposit(1000)
>     tim.show_balance()
>     tim.withdrawl(500)
>     tim.show_transactions()
> 
>     tim.show_balance()
> 
> 
> 
> Im using Ubuntu Linux. My problem is that I cannot get show_transactions
> to print out on the console. I suspect that I cannot use pytz ( as I'm
> using Python 2.7) . Im trying to get the date and time of the transaction
> (as shown on this line -
> 
> print "{:6} {} on {} (local time was {})".format(amount, tran_type, date,
> date.astimezone())
> 
> But it will. Is there a workaround for pytz, or another problem that I am
> missing?

Read the error message and traceback carefully (and remember to provide it 
in your post). It usually has important clues that help you (or us) fix what 
went wrong.

Now I recommend that you forget about the Account class for the moment, fire 
up the interactive interpreter and play around with datetime and pytz 
a bit. Once you have working building blocks you can go back and easily 
apply the lessons you learned from your experiments to the original problem. 
Spoiler below:



























>>> import datetime
>>> import pytz
>>> t = pytz.utc.localize(datetime.datetime.utcnow())
>>> t
datetime.datetime(2017, 7, 19, 21, 34, 40, 117522, tzinfo=<UTC>)
>>> t.astimezone()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Required argument 'tz' (pos 1) not found
>>> t.astimezone(pytz.timezone("MET"))
datetime.datetime(2017, 7, 19, 23, 34, 40, 117522, tzinfo=<DstTzInfo 'MET' 
MEST+2:00:00 DST>)

See? To convert to a timezone you have to actually specify the timezone you 
want.