Python Parser

The mypy parser uses the CPython "ast" module to convert source code into an abstract syntax tree (AST). (The term parse tree is sometimes used informally as a synonym.)

You can manually call the mypy.parse.parse function to experiment with it (first install test dependencies in the current virtualenv):

$ cd mypy  # mypy repo
$ python
>>> from mypy.options import Options
>>> from mypy.parse import parse
>>> parse("print('hello, world')", "hello.py", None, None, Options())
MypyFile:1(
  hello.py
  ExpressionStmt:1(
    CallExpr:1(
      NameExpr(print)
      Args(
        StrExpr(hello, world)))))

The names MypyFile, ExpressionStmt, CallExpr, NameExpr and StrExpr refer to AST node classes defined in mypy/nodes.py. The numbers after colons are line numbers.

The parser does only a minimal amount of consistency checks. As such it also accepts many invalid programs. The next compiler pass, Semantic Analyzer, performs additional checks.