symtable — Access to the compiler’s symbol tables

Source code:Lib/symtable.py


Symbol tables are generated by the compiler from AST just before bytecode isgenerated. The symbol table is responsible for calculating the scope of everyidentifier in the code.symtable provides an interface to examine thesetables.

Generating Symbol Tables

symtable.symtable(code,filename,compile_type)

Return the toplevelSymbolTable for the Python sourcecode.filename is the name of the file containing the code.compile_type islike themode argument tocompile().

Examining Symbol Tables

classsymtable.SymbolTable

A namespace table for a block. The constructor is not public.

get_type()

Return the type of the symbol table. Possible values are'class','module', and'function'.

get_id()

Return the table’s identifier.

get_name()

Return the table’s name. This is the name of the class if the table isfor a class, the name of the function if the table is for a function, or'top' if the table is global (get_type() returns'module').

get_lineno()

Return the number of the first line in the block this table represents.

is_optimized()

ReturnTrue if the locals in this table can be optimized.

is_nested()

ReturnTrue if the block is a nested class or function.

has_children()

ReturnTrue if the block has nested namespaces within it. These canbe obtained withget_children().

has_exec()

ReturnTrue if the block usesexec.

get_identifiers()

Return a list of names of symbols in this table.

lookup(name)

Lookupname in the table and return aSymbol instance.

get_symbols()

Return a list ofSymbol instances for names in the table.

get_children()

Return a list of the nested symbol tables.

classsymtable.Function

A namespace for a function or method. This class inheritsSymbolTable.

get_parameters()

Return a tuple containing names of parameters to this function.

get_locals()

Return a tuple containing names of locals in this function.

get_globals()

Return a tuple containing names of globals in this function.

get_nonlocals()

Return a tuple containing names of nonlocals in this function.

get_frees()

Return a tuple containing names of free variables in this function.

classsymtable.Class

A namespace of a class. This class inheritsSymbolTable.

get_methods()

Return a tuple containing the names of methods declared in the class.

classsymtable.Symbol

An entry in aSymbolTable corresponding to an identifier in thesource. The constructor is not public.

get_name()

Return the symbol’s name.

is_referenced()

ReturnTrue if the symbol is used in its block.

is_imported()

ReturnTrue if the symbol is created from an import statement.

is_parameter()

ReturnTrue if the symbol is a parameter.

is_global()

ReturnTrue if the symbol is global.

is_nonlocal()

ReturnTrue if the symbol is nonlocal.

is_declared_global()

ReturnTrue if the symbol is declared global with a global statement.

is_local()

ReturnTrue if the symbol is local to its block.

is_annotated()

ReturnTrue if the symbol is annotated.

New in version 3.6.

is_free()

ReturnTrue if the symbol is referenced in its block, but not assignedto.

is_assigned()

ReturnTrue if the symbol is assigned to in its block.

is_namespace()

ReturnTrue if name binding introduces new namespace.

If the name is used as the target of a function or class statement, thiswill be true.

For example:

>>>table=symtable.symtable("def some_func(): pass","string","exec")>>>table.lookup("some_func").is_namespace()True

Note that a single name can be bound to multiple objects. If the resultisTrue, the name may also be bound to other objects, like an int orlist, that does not introduce a new namespace.

get_namespaces()

Return a list of namespaces bound to this name.

get_namespace()

Return the namespace bound to this name. If more than one namespace isbound,ValueError is raised.