CODEWITHSUNDEEP
pythonabstract-syntax-tree
Yodogawa Mikio
Yodogawa Mikio

Reputation: 423

How to compile ast node in 'eval' mode

I want to create a code object that I would be able to reuse with eval later on. I need to do this based on some ast nodes I have programmatically generated, therefore I can't have code as a string passed to compile function. How to construct a valid ast node for compile? Below are couple of things I have tried:

tree = ast.parse("2+2")
exe = compile(tree.body[0], filename="", mode="eval")

TypeError: expected Expression node, got Expr

tree = ast.BinOp(left=ast.Num(n=2), right=ast.Num(n=2), op=ast.Add())
exe = compile(tree, filename="", mode="eval")

TypeError: expected Expression node, got BinOp

tree = ast.BinOp(left=ast.Num(n=2), right=ast.Num(n=2), op=ast.Add())
expr = ast.Expression(body=[tree])
ast.fix_missing_locations(expr)
exe = compile(expr, filename="", mode="eval")

TypeError: required field "lineno" missing from expr

Upvotes: 5

Views: 2110

Answers (1)

blhsing
blhsing

Reputation: 106455

Your last attempt is close, but the body of ast.Expression should be a single expression, not a list of expressions.

Change:

expr = ast.Expression(body=[tree])

to:

expr = ast.Expression(body=tree)

so that eval(exe) returns: 4

Upvotes: 5

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