18.1.1 Creating AST Objects
AST objects may be created from source code or from a parse tree.
When creating an AST object from source, different functions are used
to create the 'eval' and 'exec' forms.
- The expr() function parses the parameter source as if it were an input to "compile(source, 'file.py', 'eval')". If the parse succeeds, an AST object is created to hold the internal parse tree representation, otherwise an appropriate exception is thrown.
- The suite() function parses the parameter source as if it were an input to "compile(source, 'file.py', 'exec')". If the parse succeeds, an AST object is created to hold the internal parse tree representation, otherwise an appropriate exception is thrown.
-
This function accepts a parse tree represented as a sequence and
builds an internal representation if possible. If it can validate
that the tree conforms to the Python grammar and all nodes are valid
node types in the host version of Python, an AST object is created
from the internal representation and returned to the called. If there
is a problem creating the internal representation, or if the tree
cannot be validated, a ParserError exception is thrown. An AST
object created this way should not be assumed to compile correctly;
normal exceptions thrown by compilation may still be initiated when
the AST object is passed to compileast(). This may indicate
problems not related to syntax (such as a MemoryError
exception), but may also be due to constructs such as the result of
parsing
del f(0), which escapes the Python parser but is checked by the bytecode compiler.Sequences representing terminal tokens may be represented as either two-element lists of the form
(1, 'name')or as three-element lists of the form(1, 'name', 56). If the third element is present, it is assumed to be a valid line number. The line number may be specified for any subset of the terminal symbols in the input tree.
- This is the same function as sequence2ast(). This entry point is maintained for backward compatibility.
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Release 2.4.1, documentation updated on 30 March 2005.