Bugs and limitations

Bugs

Due to limitations in what characters can be stored in an XML document, null bytes (\x00) and other characters such as escape codes in string and byte literals get stripped, and can’t be searched for. This also means that some other string literal searches might return unexpected results because of characters being stripped in the XML:

x = b"A\x00B"

$ pyastgrep './/Constant[@value="AB"]'
myfile.py:1:5:x = b"A\x00B"

Limitations and other tools

pyastgrep is useful for grepping Python code at a fairly low level. It can be used for various refactoring or linting tasks. Some linting tasks require higher level understanding of a code base. For example, to detect use of a certain function, you need to cope with various ways that the function may be imported and used, and avoid detecting a function with the same name but from a different module. For these kinds of tasks, you might be interested in:

• Semgrep

• Fixit

If you are looking for something simpler, try:

• Simon Willison’s symbex which can extract functions/methods/classes.

If you are using this as a library, you should note that while AST works well for linting, it’s not as good for rewriting code, because AST does not contain or preserve things like formatting and comments. For a better approach, have a look at libCST.