Source code for brian2.parsing.functions

import ast
import inspect

from brian2.utils.stringtools import deindent, get_identifiers, indent

from .rendering import NodeRenderer

__all__ = [
    "AbstractCodeFunction",
    "abstract_code_from_function",
    "extract_abstract_code_functions",
    "substitute_abstract_code_functions",
]


[docs]class AbstractCodeFunction(object): """ The information defining an abstract code function Has attributes corresponding to initialisation parameters Parameters ---------- name : str The function name. args : list of str The arguments to the function. code : str The abstract code string consisting of the body of the function less the return statement. return_expr : str or None The expression returned, or None if there is nothing returned. """ def __init__(self, name, args, code, return_expr): self.name = name self.args = args self.code = code self.return_expr = return_expr def __str__(self): s = ( f"def {self.name}({', '.join(self.args)}):\n{indent(self.code)}\n return" f" {self.return_expr}\n" ) return s __repr__ = __str__
[docs]def abstract_code_from_function(func): """ Converts the body of the function to abstract code Parameters ---------- func : function, str or ast.FunctionDef The function object to convert. Note that the arguments to the function are ignored. Returns ------- func : AbstractCodeFunction The corresponding abstract code function Raises ------ SyntaxError If unsupported features are used such as if statements or indexing. """ if callable(func): code = deindent(inspect.getsource(func)) funcnode = ast.parse(code, mode="exec").body[0] elif isinstance(func, str): funcnode = ast.parse(func, mode="exec").body[0] elif func.__class__ is ast.FunctionDef: funcnode = func else: raise TypeError("Unsupported function type") if funcnode.args.vararg is not None: raise SyntaxError("No support for variable number of arguments") if funcnode.args.kwarg is not None: raise SyntaxError("No support for arbitrary keyword arguments") if len(funcnode.args.defaults): raise SyntaxError("No support for default values in functions") nodes = funcnode.body nr = NodeRenderer() lines = [] return_expr = None for node in nodes: if node.__class__ is ast.Return: return_expr = nr.render_node(node.value) break else: lines.append(nr.render_node(node)) abstract_code = "\n".join(lines) args = [arg.arg for arg in funcnode.args.args] name = funcnode.name return AbstractCodeFunction(name, args, abstract_code, return_expr)
[docs]def extract_abstract_code_functions(code): """ Returns a set of abstract code functions from function definitions. Returns all functions defined at the top level and ignores any other code in the string. Parameters ---------- code : str The code string defining some functions. Returns ------- funcs : dict A mapping ``(name, func)`` for ``func`` an `AbstractCodeFunction`. """ code = deindent(code) nodes = ast.parse(code, mode="exec").body funcs = {} for node in nodes: if node.__class__ is ast.FunctionDef: func = abstract_code_from_function(node) funcs[func.name] = func return funcs
[docs]class VarRewriter(ast.NodeTransformer): """ Rewrites all variable names in names by prepending pre """ def __init__(self, pre): self.pre = pre
[docs] def visit_Name(self, node): return ast.Name(id=self.pre + node.id, ctx=node.ctx)
[docs] def visit_Call(self, node): args = [self.visit(arg) for arg in node.args] return ast.Call( func=ast.Name(id=node.func.id, ctx=ast.Load()), args=args, keywords=[], starargs=None, kwargs=None, )
[docs]class FunctionRewriter(ast.NodeTransformer): """ Inlines a function call using temporary variables numcalls is the number of times the function rewriter has been called so far, this is used to make sure that when recursively inlining there is no name aliasing. The substitute_abstract_code_functions ensures that this is kept up to date between recursive runs. The pre attribute is the set of lines to be inserted above the currently being processed line, i.e. the inline code. The visit method returns the current line processed so that the function call is replaced with the output of the inlining. """ def __init__(self, func, numcalls=0): self.func = func self.numcalls = numcalls self.pre = [] self.suspend = False
[docs] def visit_Call(self, node): # we suspend operations during an inlining operation, then resume # afterwards, see below, so we only ever try to expand one inline # function call at a time, i.e. no f(f(x)). This case is handled # by the recursion. if self.suspend: return node # We only work with the function we're provided if node.func.id != self.func.name: return node # Suspend while processing arguments (no recursion) self.suspend = True args = [self.visit(arg) for arg in node.args] self.suspend = False # The basename is used for function-local variables basename = f"_inline_{self.func.name}_{str(self.numcalls)}" # Assign all the function-local variables for argname, arg in zip(self.func.args, args): newpre = ast.Assign( targets=[ast.Name(id=f"{basename}_{argname}", ctx=ast.Store())], value=arg, ) self.pre.append(newpre) # Rewrite the lines of code of the function using the names defined # above vr = VarRewriter(f"{basename}_") for funcline in ast.parse(self.func.code).body: self.pre.append(vr.visit(funcline)) # And rewrite the return expression return_expr = vr.visit(ast.parse(self.func.return_expr, mode="eval").body) self.pre.append( ast.Assign( targets=[ast.Name(id=basename, ctx=ast.Store())], value=return_expr ) ) # Finally we replace the function call with the output of the inlining newnode = ast.Name(id=basename) self.numcalls += 1 return newnode
[docs]def substitute_abstract_code_functions(code, funcs): """ Performs inline substitution of all the functions in the code Parameters ---------- code : str The abstract code to make inline substitutions into. funcs : list, dict or set of AbstractCodeFunction The function substitutions to use, note in the case of a dict, the keys are ignored and the function name is used. Returns ------- code : str The code with inline substitutions performed. """ if isinstance(funcs, (list, set)): newfuncs = dict() for f in funcs: newfuncs[f.name] = f funcs = newfuncs code = deindent(code) lines = ast.parse(code, mode="exec").body # This is a slightly nasty hack, but basically we just check by looking at # the existing identifiers how many inline operations have already been # performed by previous calls to this function ids = get_identifiers(code) funcstarts = {} for func in funcs.values(): subids = {id for id in ids if id.startswith(f"_inline_{func.name}_")} subids = {id.replace(f"_inline_{func.name}_", "") for id in subids} alli = [] for subid in subids: p = subid.find("_") if p > 0: subid = subid[:p] i = int(subid) alli.append(i) if len(alli) == 0: i = 0 else: i = max(alli) + 1 funcstarts[func.name] = i # Now we rewrite all the lines, replacing each line with a sequence of # lines performing the inlining newlines = [] for line in lines: for func in funcs.values(): rw = FunctionRewriter(func, funcstarts[func.name]) line = rw.visit(line) newlines.extend(rw.pre) funcstarts[func.name] = rw.numcalls newlines.append(line) # Now we render to a code string nr = NodeRenderer() newcode = "\n".join(nr.render_node(line) for line in newlines) # We recurse until no changes in the code to ensure that all functions # are expanded if one function refers to another, etc. if newcode == code: return newcode else: return substitute_abstract_code_functions(newcode, funcs)