How to modify the local namespace in python

by

You’ve a couple of options. First, note that g in your example isn’t actually a local to the function (ie. not assigned within it), it’s a global (ie hasn’t been assigned to a local variable). This means that it will be looked up in the module the function is defined in. This is fortunate, as there’s no way of altering locals externally (short of patching the bytecode), as they get assigned when the function runs, not before.

One option is simply to inject your function into the function’s module’s namespace. This will work, but will affect every function in that module that accesses the variable, rather than just the one function.

To affect just the one function, you need to instead point that func_globals somewhere else. Unfortunately, this is a read-only property, but you can do what you want by recreating the function with the same body, but a different global namespace:

import new
f = new.function(f.func_code, {'g': my_g_function}, f.func_name, f.func_defaults, f.func_closure)

f will now be indentical, except that it will look for globals in the provided dict. Note that this rebinds the whole global namespace – if there are variables there that f does look up, make sure you provide them too. This is also fairly hacky though, and may not work on versions of python other than cpython.

More Related Contents:

  1. Namespaces with Module Imports
  2. What does if __name__ == "__main__": do?
  3. What does __all__ mean in Python?
  4. Visibility of global variables in imported modules
  5. What exactly does “import *” import?
  6. How do I create a namespace package in Python?
  7. Python ElementTree module: How to ignore the namespace of XML files to locate matching element when using the method “find”, “findall”
  8. type object ‘datetime.datetime’ has no attribute ‘datetime’
  9. Remove namespace and prefix from xml in python using lxml
  10. Python worker failed to connect back
  11. Python: NameError: global name ‘foobar’ is not defined [duplicate]
  12. Django: “projects” vs “apps”
  13. How to make a local variable (inside a function) global [duplicate]
  14. Is it bad practice to use a built-in function name as an attribute or method identifier?
  15. Creating a class within a function and access a function defined in the containing function’s scope
  16. What does “Symbol not found / Expected in: flat namespace” actually mean?
  17. What are Python namespaces all about
  18. inspect.getmembers() vs __dict__.items() vs dir()
  19. What does if __name__ == “__main__”: do in Python?
  20. Python: Why should ‘from import *’ be prohibited?
  21. socket.error:[errno 99] cannot assign requested address and namespace in python
  22. How can a name be “unbound” in Python? What code can cause an `UnboundLocalError`?
  23. How to find “import name” of any package in Python?
  24. Python: Name resolution; order of function def’s
  25. Python modules with identical names (i.e., reusing standard module names in packages)
  26. Python: deleting a class attribute in a subclass
  27. NameError: global name is not defined
  28. argparse subcommands with nested namespaces
  29. How do I parse and write XML using Python’s ElementTree without moving namespaces around?
  30. lxml: add namespace to input file

Leave a Comment