Python 3-在OOP中搜索

Question

I'm fairly new to programming and have been self teaching myself python in my free time. I'm really trying to under stand OOP and have hit a wall. This is a smaller example of a larger program I am writing.

class Emp():
    def __init__(self, first, last, age):
        self.first = first
        self.last = last
        self.age = age

    def PrintEmp(self):
        return (self.first, self.last, self.age)

employee = {}

employee[0] = {'Info': {'First': 'Jacob', 'Last': 'Jones', 'Age': 31}}
employee[1] = {'Info': {'First': 'Joe', 'Last': 'Smith', 'Age': 45}}
employee[2] = {'Info': {'First': 'Jim', 'Last': 'Bob', 'Age': 38}}
employee[3] = {'Info': {'First': 'Jack', 'Last': 'Black', 'Age': 21}}
employee[4] = {'Info': {'First': 'Joey', 'Last': 'John', 'Age': 39}}
employee[5] = {'Info': {'First': 'Job', 'Last': 'God', 'Age': 99}}

for key in employee:
    employee[key]['Info']['First'] = Emp(employee[key]['Info']['First'],
                                     employee[key]['Info']['Last'],
                                     employee[key]['Info']['Age'])

choice = input('Employee')

for key in employee:
    if choice == employee[key]['Info']['First']:
        print(choice.PrintEmp)
        #choice.first, choice.last, choice.age ect...
    else:
        print("This isn't working")

I am basically trying to search through a list of known employees and then print anything from the actual object or just search directly through the objects for specific attributes.

Answer 1

choice probably wont match anything because you're comparing the user input string to an Emp instance.

If you removed:

for key in employee:
    employee[key]['Info']['First'] = Emp(employee[key]['Info']['First'],
                                     employee[key]['Info']['Last'],
                                     employee[key]['Info']['Age'])

You should be able to at least iterate through and match employees based on First name.

---

As for OOP, I would recommend starting at SOLID, which are 5 design principles and provide a great guideline for OOP development.

https://en.wikipedia.org/wiki/SOLID_(object-oriented_design)

I think their strongest suite is that they give us some concepts to evaluate code by, and give us a place to start talking, and provide us with shared terminology.

---

2 amazingly useful concepts of programming and OOP are: encapsulation and delegation.

I could imagine a collection of employees that exposes a search() method. This would insulate your main code from having to change as your improve/change your search implementation and it isolates search logic to only parts of the program that require to know the specifics of it.

Answer 2

Welcome to programming! I started teaching myself a little under a year ago, so I can relate to any frustrations that may arise when learning a new concept.

I'll start with what you're trying to accomplish first - invoking your PrintEmp method of an Emp instance. The reason your current code isn't working as you would like is because you're iterating through every employee (When I think you really just want to find a match), and then your condition will never evaluate as intended because choice is a str object and your keys in employee are integers. In the following example I start by grabbing the dictionary containing the needed values to create an instance of Emp with info = value['Info'] . Of the dictionary now stored in the variable info I can grab the values I need with info.values() and then I unpack those values as arguments for each Emp instance that is created. Now that each dictionary has been converted to an Emp object we can call PrintEmp as we'd like.

Note: I took the liberty of changing your naming of the dictionary employee to employees as it's a bit more accurate.

# Here we instantiate each `employee`
for key, value in employees.items():
    info = value['Info']  # e.g. here I now have {'First': 'Jacob', 'Last': 'Jones', 'Age': 31}

    # Now I am going to create an `Emp` instance for each dictionary in `employees`
    employees[key] = Emp(*info.values())

choice = int(input('Enter an employee index: '))

if choice in employees:
    print(employees[choice].PrintEmp())
else:
    "That still isn't working..."

Running the program now:

>>> Enter an employee index: 2
returning: ('Jim', 'Bob', 38)

Say you wanted to format the output of your PrintEmp method - you can use the str.format method like so:

def PrintEmp(self):
    # Note the type conversion for self.age
    return "Hi my name is {} {}, and I'm {}!".format(self.first, self.last, str(self.age))

Running the program now:

>>> Enter an employee index: 2
returning: Hi my name is Jim Bob, and I'm 38!

If there's anything you would like clarification on, don't hesitate to ask!

Answer 3

As already noted by dm03514 your if-condition did not work, because you were comparing a string with a class instance.

Next issue, PrintEmp() is a function of Emp and not choice, therefore print(choice.PrintEmp) does not work.

You may want to try this:

class Emp():
    def __init__(self, first, last, age):
        self.first = first
        self.last = last
        self.age = age

    def PrintEmp(self):
        return (self.first, self.last, self.age)

employee = {}

employee[0] = {'Info': {'First': 'Jacob', 'Last': 'Jones', 'Age': 31}}
employee[1] = {'Info': {'First': 'Joe', 'Last': 'Smith', 'Age': 45}}
employee[2] = {'Info': {'First': 'Jim', 'Last': 'Bob', 'Age': 38}}
employee[3] = {'Info': {'First': 'Jack', 'Last': 'Black', 'Age': 21}}
employee[4] = {'Info': {'First': 'Joey', 'Last': 'John', 'Age': 39}}
employee[5] = {'Info': {'First': 'Job', 'Last': 'God', 'Age': 99}}


employees = []
for key in employee:
    employees.append(
        Emp(
            employee[key]['Info']['First'],
            employee[key]['Info']['Last'],
            employee[key]['Info']['Age']
        )
    )

choice = input('Employee first name:\n')

for employee in employees:
    if choice == employee.first:
        print (employee.PrintEmp())
    else:
        print("This isn't working")

Returns for 'Jim':

This isn't working
This isn't working
('Jim', 'Bob', 38)
This isn't working
This isn't working
This isn't working