python ast module fails in pydev, succeeds in cmdline python

Question

This is weird. I run this program in PyDev

import ast
import sys

if __name__ == '__main__':
    print sys.version
    src = '''
print 3*4+5**2
'''
    print dir(ast)
    n = ast.parse(src)
    print n

and it outputs:

2.7.5 |Anaconda 1.6.0 (64-bit)| (default, May 31 2013, 10:45:37) [MSC v.1500 64 bit (AMD64)]
['__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__']
Traceback (most recent call last):
  File ["C:\research\ast\ast\test1.py", line 16, in <module>
    n = ast.parse(src)
AttributeError: 'module' object has no attribute 'parse'

but when I run it in cmdline it prints this:

C:\research\ast\ast>python test1.py
2.7.5 |Anaconda 1.6.0 (64-bit)| (default, May 31 2013, 10:45:37) [MSC v.1500 64
bit (AMD64)]
['AST', 'Add', 'And', 'Assert', 'Assign', 'Attribute', 'AugAssign', 'AugLoad', '
AugStore', 'BinOp', 'BitAnd', 'BitOr', 'BitXor', 'BoolOp', 'Break', 'Call', 'Cla
ssDef', 'Compare', 'Continue', 'Del', 'Delete', 'Dict', 'DictComp', 'Div', 'Elli
psis', 'Eq', 'ExceptHandler', 'Exec', 'Expr', 'Expression', 'ExtSlice', 'FloorDi
v', 'For', 'FunctionDef', 'GeneratorExp', 'Global', 'Gt', 'GtE', 'If', 'IfExp',
'Import', 'ImportFrom', 'In', 'Index', 'Interactive', 'Invert', 'Is', 'IsNot', '
LShift', 'Lambda', 'List', 'ListComp', 'Load', 'Lt', 'LtE', 'Mod', 'Module', 'Mu
lt', 'Name', 'NodeTransformer', 'NodeVisitor', 'Not', 'NotEq', 'NotIn', 'Num', '
Or', 'Param', 'Pass', 'Pow', 'Print', 'PyCF_ONLY_AST', 'RShift', 'Raise', 'Repr'
, 'Return', 'Set', 'SetComp', 'Slice', 'Store', 'Str', 'Sub', 'Subscript', 'Suit
e', 'TryExcept', 'TryFinally', 'Tuple', 'UAdd', 'USub', 'UnaryOp', 'While', 'Wit
h', 'Yield', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '
__version__', 'alias', 'arguments', 'boolop', 'cmpop', 'comprehension', 'copy_lo
cation', 'dump', 'excepthandler', 'expr', 'expr_context', 'fix_missing_locations
', 'get_docstring', 'increment_lineno', 'iter_child_nodes', 'iter_fields', 'keyw
ord', 'literal_eval', 'mod', 'operator', 'parse', 'slice', 'stmt', 'unaryop', 'w
alk']
<_ast.Module object at 0x0000000002A99EB8>

What could be going wrong?

Answer 1

It seems the ast you have imported in PyDev is not the ast module in the standard library, but a package.

I guess:

There is a __init__.py file in the same directory as your test1.py.
You selected "Add project directory to the PYTHONPATH" during the project creation.

These two combined, results in that error. The ast module in the standard library is shadowed by this ast package.

In cmdline python, this ast package is not in the search path, thus the ast module is imported.

If you change test1.py to

import ast

if __name__ == '__main__':
    print ast.__file__

I guess the output in PyDev would be

C:\research\ast\ast\__init__.pyc