Python create instance of class using string manipulation

Question

I wrote Class and created two lists. The first for the users and the second for the user-attributes.

I would now like to loop trough the two lists in order to create multiple Class instances with the respective data.

class Employee:
    
    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'


emp_1 = Employee('Corey', 'Schafer', '50000')
emp_2 = Employee('Test', 'User', '60000')

by printing print(amp_1.email) i can create the instance of the class:

will print [email protected]

Now i dont want to write it out manually so i want to loop trough it:

for user in users:
    for user_atr in user_atrs:
        print(user + '.' + user_atr)

will print:

empy_1.first
empy_1.last
empy_1.pay
empy_1.email
empy_2.first
empy_2.last
empy_2.pay
empy_2.email

Instead of:

Corey
Schafer
50000
[email protected]
Test
User
60000
[email protected]

How can i use that loop to actually create the instance of the class and not just the blueprint?

azro · Accepted Answer · 2020-10-17 15:06:38Z

3

Basic Solution

a list of string of the users : ['emp_1', 'emp_2']
a list of string that are attributs name ['first', 'last', 'pay', 'email']

Then use the builtin method globals() to get the variable and getattr(obj, name, default) but that isn't nice and requires to type variable names

emp_1 = Employee('Corey', 'Schafer', 50000)
emp_2 = Employee('Test', 'User', '60000')

for user in ['emp_1', 'emp_2']:
    for user_atr in ['first', 'last', 'pay', 'email']:
        print(getattr(globals()[user], user_atr))

Better Solution

a list of Employee instances : [emp_1, emp_2]
Access object properties with __dict__ (key is name, value are property's value)

for user in [emp_1, emp_2]:
    for user_atr in user.__dict__.values():
        print(user_atr)

Corey
Schafer
50000
[email protected]
...

To read both name and value at the same time

for user in [emp_1, emp_2]:
    for user_atr in user.__dict__.items():
        print(user_atr)

('first', 'Corey')
('last', 'Schafer')
('pay', 50000)
('email', '[email protected]')
...

edited Oct 17, 2020 at 15:06

answered Oct 17, 2020 at 14:51

azro

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1 Comment

Barry Over a year ago

Jesus, i didn't. I was completely blind. Sorry!! Of course

Ollie Pugh · Accepted Answer · 2020-10-17 14:57:35Z

class Employee:
    
    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'


emp_1 = Employee('Corey', 'Schafer', '50000')
emp_2 = Employee('Test', 'User', '60000')

users = {"emp_1": emp_1,
    "emp_2": emp_2}

for user in users.values():
    for attribute in list(user.__dict__.keys()):
        print(f"{name}.{attribute}")

This will do that for you by storing the users in a dictionary with the name of the user as the dictionary key and then using the __dict__ attribute from the Employee class to get a dictionary of all atributes and then printing the name of each attribute from that dictionary.

If you are trying to print the value of each of these attributes then it can be changed to the following:

users = {"emp_1": emp_1,
    "emp_2": emp_2}

for name, user in users.items():
    for attribute in list(user.__dict__.keys()):
        print(getattr(user,attribute))

Using this method means that any more attributes added to the employee class will be printed also.

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