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c#pythonpython-2.7
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Reputation: 1103

Mimic C# classes in Python

I have the following C# public classes:

public class ClassA
{
    public byte var1;
    public TypeX var2;
}


public class TypeX
{
    public UInt16 num1;
    public UInt32 num2;
}

(Names are simplified for this example and are not real)

What would this look like in Python? Specifically, how would var2 be created as an instance of TypeX?

So far I have the come up with the following Python classes:

class ClassA():
    def __init__(self, var1, var2 = TypeX):
        self.var1 = var1
        self.var2 = var2


class TypeX():
    def __init__(self, num1, num2):
        self.num1 = num1
        self.num2 = num2

However, I am nearly 100% sure this is not correct. Should ClassA inherit TypeX? Any guidance or explanations would be appreciated!

Upvotes: 0

Views: 127

Answers (3)

Matias Cicero
Matias Cicero

Reputation: 26281

Python is not a statically typed language, so the answer to:

How can I enforce var2 to be of type TypeX?

is you don't. Of course, you can type-check something, but the Python interpreter won't do it for you, you'll need to explicitly write this rule on your code programatically.

As to the question of how the following:

public class ClassA
{
    public byte var1;
    public TypeX var2;
}


public class TypeX
{
    public UInt16 num1;
    public UInt32 num2;
}

translates to Python, the answer is as simple as:

# You need to explicitly initialize the variables to their correspondent default values
class ClassA(object):
    def __init__(self):
        self.var1 = bytes() # or b''
        self.var2 = None

class TypeX(object):
    def __init__(self):
        self.num1 = int() # or 0
        self.num2 = int() # or 0

Upvotes: 1

blhsing
blhsing

Reputation: 106618

Python is a dynamically-typed language. The type of a variable is not determined until it is assigned a value.

The closest you can get to your C# code would be to use type hints, supported in Python 3.5+:

class TypeX:
    def __init__(self, num1, num2):
        self.num1 = num1
        self.num2 = num2

class ClassA:
    def __init__(self, var1, var2: TypeX):
        self.var1 = var1
        self.var2 = var2

But even with type hints, the type of var2 will not be enforced either at compilation time or at run time.

Upvotes: 2

Chris
Chris

Reputation: 136977

Python is dynamically, not statically, typed, so

class ClassA():
    def __init__(self, var1, var2):
        self.var1 = var1
        self.var2 = var2


class TypeX():
    def __init__(self, num1, num2):
        self.num1 = num1
        self.num2 = num2

is a reasonable thing to do. Just pass an instance of TypeX in when you instantiate your ClassA.

However, as of Python 3.5, you can add optional type hints, e.g.

class TypeX():
    def __init__(self, num1, num2):
        self.num1 = num1
        self.num2 = num2


class ClassA():
    def __init__(self, var1, var2: TypeX):
        self.var1 = var1
        self.var2 = var2

This doesn't affect how the code runs (in particular it doesn't enforce the type at runtime), but it can help developers, and their tools, understand the code better.

Tools like mypy can be used to statically check your code using these optional type hints, especially if you add them to your test suite. The more hints you add, the more mypy can help.

Upvotes: 1

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