alcarithemad / typetrace

Trace Python execution and record type information.

typetrace

Trace Python execution and record type information for function calls. Produces type annotations which strongly resemble PEP 484 "type comments". Probably works in Python 2 and 3.

Usage

import typetrace
tt = typetrace.TypeTracer()

...

# start tracing
tt.set_trace()

# do some interesting stuff here
# consider invoking a test suite, or large sample application

# end tracing
tt.end_trace()

# print traced type annotations
tt.print_types()

# or write them to a file by passing a file object to tt.write_types(f)

Output looks like this:

lib/python2.7/inspect.py:155 isgeneratorfunction   # type: (Callable) -> bool
lib/python2.7/UserDict.py:103 __contains__     # type: (str) -> bool
lib/python2.7/UserDict.py:91 get   # type: (str, Union[None, int]) -> Union[None, int]
lib/python2.7/encodings/__init__.py:49 normalize_encoding      # type: (str) -> str
lib/python2.7/encodings/__init__.py:71 search_function # type: (str) -> Tuple[Callable, Callable, classobj, classobj]
lib/python2.7/encodings/utf_8.py:15 decode     # type: (Union[buffer, str], str) -> Tuple[unicode, int]
lib/python2.7/encodings/utf_8.py:33 getregentry        # type: () -> Tuple[Callable, Callable, classobj, classobj]
lib/python2.7/posixpath.py:120 dirname # type: (str) -> str
lib/python2.7/posixpath.py:329 normpath        # type: (str) -> str
lib/python2.7/posixpath.py:358 abspath # type: (str) -> str
lib/python2.7/posixpath.py:52 isabs    # type: (str) -> bool
lib/python2.7/posixpath.py:82 split    # type: (str) -> Tuple[str, str]
lib/python2.7/re.py:138 match  # type: (str, str, int) -> Union[SRE_Match, None]
lib/python2.7/re.py:148 sub    # type: (str, str, str, int, int) -> str
lib/python2.7/re.py:192 compile        # type: (str, int) -> SRE_Pattern
lib/python2.7/re.py:230 _compile       # type: (*Union[str, int]) -> SRE_Pattern

Caveats

It works, but:

• It's slow.
• It may generate some nonsensical type annotations.
• It only outputs the Python 2 compatible type comment syntax.
• If you want to add the generated annotations to the source automatically, you'll need to write more code.
• Did I mention it's slow?
• It doesn't handle functions returning multiple lengths of tuples very well. It produces a union of each length it's seen.
• Doesn't simplify Union[T, None] to Optional[T].
• It's poorly tested.
• Things that raise exceptions will include None among their return types, even if None is never otherwise returned.
• Probably doesn't handle @classmethod correctly.

License

MIT license.