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Really simple C++ code generation in Python

, 3 Apr 2013
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Quickly churn out repetitive C++, C#, or Java code from any data that Python can read.

Introduction

You're allergic to learning curves and want to get your code generated now! Here's an easily customized 100-line Python module just a notch above f.writeline.

Using the code

Let's start with a really simple example (no pointing out that main returns int please! It's an example.)

from CodeGen import *
 
cpp = CppFile("test.cpp")
 
cpp("#include <iostream>")
 
with cpp.block("void main()"):
    for i in range(5):
        cpp('std::cout << "' + str(i) + '" << std::endl;')
    
cpp.close()

The output:

#include <iostream>
void main()
{
    std::cout << "0" << std::endl;
    std::cout << "1" << std::endl;
    std::cout << "2" << std::endl;
    std::cout << "3" << std::endl;
    std::cout << "4" << std::endl;
}

Leveraging Python's with keyword we can encapsulate statements in {} blocks which get closed out automatically, with the correct indentation so that the output remains human-readable.

Substitutions

When generating more sophisticated code, you'll quickly realize your Python script becomes progressively less readable with ugly string concatenations all over the place. That's where the subs method come in:

from CodeGen import *
 
cpp = CppFile("test.cpp")
 
cpp("#include <iostream>")
 
with cpp.block("void main()"):
    for i in range(5):
        with cpp.subs(i=str(i), xi="x"+str(i+1)):
            cpp('int $xi$ = $i$;')
    
cpp.close()

which produces:

#include <iostream>

void main()
{
    int x1 = 0;
    int x2 = 1;
    int x3 = 2;
    int x4 = 3;
    int x5 = 4;
}

The substitutions are valid within the Python with block, which can be nested.

That's pretty much it

To finish off here's a more complicated example to generate the following code:

class ClassX
{
protected:
    A a;
    B b;
    C c;
public:
    ClassX(A a, B b, C c)
    {
        this->a = a;
        this->b = b;
        this->c = c;
    }
    A getA()
    {
        return this->a;
    }
    B getB()
    {
        return this->b;
    }
    C getC()
    {
        return this->c;
    }
};
class ClassY
{
protected:
    P p;
    Q q;
public:
    ClassY(P p, Q q)
    {
        this->p = p;
        this->q = q;
    }
    P getP()
    {
        return this->p;
    }
    Q getQ()
    {
        return this->q;
    }
};

Take a look at CodeGen.py to see how the label function is implemented for a hint on how to extend the code with language-specific features.

from CodeGen import *
 
cpp = CppFile("test.cpp")
 
CLASS_NAMES = ["ClassX", "ClassY"]
VAR_NAMES = { "ClassX": ["A", "B", "C"], 
                      "ClassY": ["P","Q"] }
 
for className in CLASS_NAMES:
    with cpp.subs(ClassName=className):
        with cpp.block("class $ClassName$", ";"):
            cpp.label("protected")
            for varName in VAR_NAMES[className]:
                with cpp.subs(A=varName, a=varName.lower()):
                    cpp("$A$ $a$;")
            cpp.label("public")
            with cpp.subs(**{"A a": ", ".join([x + " " + x.lower() for x in VAR_NAMES[className]])}):
                with cpp.block("$ClassName$($A a$)"):
                    for varName in VAR_NAMES[className]:
                        with cpp.subs(a=varName.lower()):
                            cpp("this->$a$ = $a$;")
            for varName in VAR_NAMES[className]:
                with cpp.subs(A=varName, a=varName.lower(), getA="get"+varName):
                    with cpp.block("$A$ $getA$()"):
                        cpp("return this->$a$;")
    
cpp.close()

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Eric Reynolds

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Comments and Discussions

 
QuestionI don't seem to be able to view the code PinmemberMember 1094921215-Jul-14 17:06 
AnswerRe: I don't seem to be able to view the code PinmemberMember 1098083830-Jul-14 2:42 
GeneralMy vote of 5 PinmemberMihai MOGA10-May-13 18:37 
GeneralMy vote of 5 Pinmembermorgr7-Apr-13 23:13 
GeneralMy vote of 1 PinmemberAli Khanlarkhani5-Apr-13 20:25 
GeneralRe: My vote of 1 PinmemberEric Reynolds5-Apr-13 20:40 
GeneralRe: My vote of 1 PinmemberAli Khanlarkhani5-Apr-13 21:13 
GeneralRe: My vote of 1 PinmemberEric Reynolds6-Apr-13 3:32 

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