Is there a generic way for a function to reference itself?
Question:
I can access a python function’s attribute inside of function itself by below code:
def aa():
print aa.__name__
print aa.__hash__
# other simliar
However, if above aa()
function is a template for write other code, say bb()
, I have to write:
def bb():
print bb.__name__
print bb.__hash__
# other simliar
Is there a “pointer” similar to the self
argument in a class method so I could write code like this?
def whatever():
print self.__name__
print self.__hash__
# other simliar
I searched and found someone said to use the class to solve this problem, but that may be a trouble to redefine all the existing functions. Any suggestions?
Answers:
http://docs.python.org/library/inspect.html looks promising:
import inspect
def foo():
felf = globals()[inspect.getframeinfo(inspect.currentframe()).function]
print felf.__name__, felf.__doc__
you can also use the sys
module to get the name of the current function:
import sys
def bar():
felf = globals()[sys._getframe().f_code.co_name]
print felf.__name__, felf.__doc__
There is no generic way for a function to refer to itself. Consider using a decorator instead. If all you want as you indicated was to print information about the function that can be done easily with a decorator:
from functools import wraps
def showinfo(f):
@wraps(f)
def wrapper(*args, **kwds):
print(f.__name__, f.__hash__)
return f(*args, **kwds)
return wrapper
@showinfo
def aa():
pass
If you really do need to reference the function, then just add it to the function arguments:
def withself(f):
@wraps(f)
def wrapper(*args, **kwds):
return f(f, *args, **kwds)
return wrapper
@withself
def aa(self):
print(self.__name__)
# etc.
Edit to add alternate decorator:
You can also write a simpler (and probably faster) decorator that will make the wrapped function work correctly with Python’s introspection:
def bind(f):
"""Decorate function `f` to pass a reference to the function
as the first argument"""
return f.__get__(f, type(f))
@bind
def foo(self, x):
"This is a bound function!"
print(self, x)
>>> foo(42)
<function foo at 0x02A46030> 42
>>> help(foo)
Help on method foo in module __main__:
foo(self, x) method of builtins.function instance
This is a bound function!
This leverages Python’s descriptor protocol: functions have a __get__
method that is used to create bound methods. The decorator simply uses the existing method to make the function a bound method of itself. It will only work for standalone functions, if you wanted a method to be able to reference itself you would have to do something more like the original solution.
How about a quick hack to make your own “self” name, like this:
>>> def f():
... self = f
... print "My name is ", self.__name__, "and I am", self.__hash__
...
>>> f()
My name is f and I am <method-wrapper '__hash__' of function object at 0x00B50F30>
>>> x = f
>>> x()
My name is f and I am <method-wrapper '__hash__' of function object at 0x00B50F30>
>>>
You can at least say self = bb
in the first line, and then you only need to change that line when you change the function name, instead of every other reference.
My code editor highlights the variable self
the same way it does for classes, too.
I can access a python function’s attribute inside of function itself by below code:
def aa():
print aa.__name__
print aa.__hash__
# other simliar
However, if above aa()
function is a template for write other code, say bb()
, I have to write:
def bb():
print bb.__name__
print bb.__hash__
# other simliar
Is there a “pointer” similar to the self
argument in a class method so I could write code like this?
def whatever():
print self.__name__
print self.__hash__
# other simliar
I searched and found someone said to use the class to solve this problem, but that may be a trouble to redefine all the existing functions. Any suggestions?
http://docs.python.org/library/inspect.html looks promising:
import inspect
def foo():
felf = globals()[inspect.getframeinfo(inspect.currentframe()).function]
print felf.__name__, felf.__doc__
you can also use the sys
module to get the name of the current function:
import sys
def bar():
felf = globals()[sys._getframe().f_code.co_name]
print felf.__name__, felf.__doc__
There is no generic way for a function to refer to itself. Consider using a decorator instead. If all you want as you indicated was to print information about the function that can be done easily with a decorator:
from functools import wraps
def showinfo(f):
@wraps(f)
def wrapper(*args, **kwds):
print(f.__name__, f.__hash__)
return f(*args, **kwds)
return wrapper
@showinfo
def aa():
pass
If you really do need to reference the function, then just add it to the function arguments:
def withself(f):
@wraps(f)
def wrapper(*args, **kwds):
return f(f, *args, **kwds)
return wrapper
@withself
def aa(self):
print(self.__name__)
# etc.
Edit to add alternate decorator:
You can also write a simpler (and probably faster) decorator that will make the wrapped function work correctly with Python’s introspection:
def bind(f):
"""Decorate function `f` to pass a reference to the function
as the first argument"""
return f.__get__(f, type(f))
@bind
def foo(self, x):
"This is a bound function!"
print(self, x)
>>> foo(42)
<function foo at 0x02A46030> 42
>>> help(foo)
Help on method foo in module __main__:
foo(self, x) method of builtins.function instance
This is a bound function!
This leverages Python’s descriptor protocol: functions have a __get__
method that is used to create bound methods. The decorator simply uses the existing method to make the function a bound method of itself. It will only work for standalone functions, if you wanted a method to be able to reference itself you would have to do something more like the original solution.
How about a quick hack to make your own “self” name, like this:
>>> def f():
... self = f
... print "My name is ", self.__name__, "and I am", self.__hash__
...
>>> f()
My name is f and I am <method-wrapper '__hash__' of function object at 0x00B50F30>
>>> x = f
>>> x()
My name is f and I am <method-wrapper '__hash__' of function object at 0x00B50F30>
>>>
You can at least say self = bb
in the first line, and then you only need to change that line when you change the function name, instead of every other reference.
My code editor highlights the variable self
the same way it does for classes, too.