Scratch3.0 secondary development with blocks to generate python code

Before we begin, let's review the previously written article "Thescratch3.0 secondary development of blocks to generate code ideas", in the article probably wrote a few steps to generate code, the reader may not understand, this is based on my development experience. Now specifically write the realization of the method.

I. Introducing a file to generate code

For example, to generate arduino code, you have to introduce the file that generates arduino code, and to generate python code, you have to introduce the python file.

This generator file is imported from Blockly, on which scratch-blocks is based. The current scratch-blocks does not have a generators directory, which can be copied from blockly.
Analyze blockly's code specifically:

 = new ('Python');

An instance of python is that will call methods in generator;

(...);

What this method does is add keywords to python, and blockly's python file already has many python keywords set up in it.

.ORDER_ATOMIC = 0;            // 0 "" ...
.ORDER_COLLECTION = 1;        // tuples, lists, dictionaries
.ORDER_STRING_CONVERSION = 1; // `expression...`
.ORDER_MEMBER = 2.1;          // . []
.ORDER_FUNCTION_CALL = 2.2;   // ()
.ORDER_EXPONENTIATION = 3;    // **
.ORDER_UNARY_SIGN = 4;        // + -
.ORDER_BITWISE_NOT = 4;       // ~
.ORDER_MULTIPLICATIVE = 5;    // * / // %
.ORDER_ADDITIVE = 6;          // + -
.ORDER_BITWISE_SHIFT = 7;     // << >>
.ORDER_BITWISE_AND = 8;       // &
.ORDER_BITWISE_XOR = 9;       // ^
.ORDER_BITWISE_OR = 10;       // |
.ORDER_RELATIONAL = 11;       // in, not in, is, is not,
                                            //     <, <=, >, >=, <>, !=, ==
.ORDER_LOGICAL_NOT = 12;      // not
.ORDER_LOGICAL_AND = 13;      // and
.ORDER_LOGICAL_OR = 14;       // or
.ORDER_CONDITIONAL = 15;      // if else
.ORDER_LAMBDA = 16;           // lambda
.ORDER_NONE = 99;             // (...)

The above code sets the priority.
See blockly's python file for other methods.

II. Define the generated python code

The generated code needs to be defined for each block.

1. Get the type of the block

Blocks are distinguished by type, and the type of each block is unique. scratch-blocks' basic blocks are defined in the scratch-blocks\blocks_vertical directory.
For details, check out the previous blog, "TheScratch3.0 secondary development of scratch-blocks in the blocks of the type, definition and use of methods》

The following is the definition of a block of type "motion_movesteps".

['motion_movesteps'] = {
  /**
   * Block to move steps.
   * @this 
   */
  init: function() {
    ({
      "message0": .MOTION_MOVESTEPS,
      "args0": [
        {
          "type": "input_value",
          "name": "STEPS"
        }
      ],
      "category": ,
      "extensions": ["colours_motion", "shape_statement"]
    });
  }
};

Defines the generated python statements:

 ['motion_movesteps'] = function (block) {
        var steps = (block, "STEPS", .ORDER_NONE);
        return 'move ' + steps + ' steps\n';
    };

2、Get the value of the parameter

Depending on the type of the parameter, choose, or to get the value.

3, from xml to parse the composition of a block structure

This is the xml structure of the motion_movesteps block, it consists of two blocks, "motion_movesteps" and "math_number", and the shadow is also a block.

<block type="motion_movesteps">
            <value name="STEPS">
                <shadow type="math_number">
                    <field name="NUM">10</field>
                </shadow>
            </value>
        </block>

So in addition to the "motion_movesteps" generated python statement defined above, you also need to define the math_number generated statement.

['math_number'] = function(block) {
  // Numeric value.
  var code = parseFloat(('NUM'));
  var order;
  if (code == Infinity) {
    code = 'float("inf")';
    order = .ORDER_FUNCTION_CALL;
  } else if (code == -Infinity) {
    code = '-float("inf")';
    order = .ORDER_UNARY_SIGN;
  } else {
    order = code < 0 ? .ORDER_UNARY_SIGN :
            .ORDER_ATOMIC;
  }
  return [code, order];
}

4. According to the shape of the block to set the data type of return

geometry	Type of return
	string (computer science)
	string (computer science)
	[code, order] array
	[code, order] array

Introduce the module: .definitions_[module name] = "import xxxx";
Declare the function: .definitions_[module name] = "def xxx ...";

III. Generating python code

In the scratch-gui/src/containers/ file, add a listen to the workspace

 ();

IV. Conclusion

This article mainly introduces the blocks to generate python code methods, due to limited space, write is not very comprehensive, but probably generate these methods. If you encounter problems in the development process, you can private message me to leave me a message, I try to help you solve the problem!

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