patsy/patsy/parse_formula.py at master · Python-Repository-Hub/patsy · GitHub

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# This file is part of Patsy

# See file LICENSE.txt for license information.

# This file defines a parser for a simple language based on S/R "formulas"

# (which are described in sections 2.3 and 2.4 in Chambers & Hastie, 1992). It

# uses the machinery in patsy.parse_core to do the heavy-lifting -- its

# biggest job is to handle tokenization.

from __future__ import print_function

__all__ = ["parse_formula"]

# The Python tokenizer

import tokenize

import six

from six.moves import cStringIO as StringIO

from patsy import PatsyError

from patsy.origin import Origin

from patsy.infix_parser import Token, Operator, infix_parse, ParseNode

from patsy.tokens import python_tokenize, pretty_untokenize

from patsy.util import PushbackAdapter

_atomic_token_types = ["PYTHON_EXPR", "ZERO", "ONE", "NUMBER"]

def _is_a(f, v):

try:

f(v)

except ValueError:

return False

else:

return True

# Helper function for _tokenize_formula:

def _read_python_expr(it, end_tokens):

# Read out a full python expression, stopping when we hit an

# unnested end token.

pytypes = []

token_strings = []

origins = []

bracket_level = 0

for pytype, token_string, origin in it:

assert bracket_level >= 0

if bracket_level == 0 and token_string in end_tokens:

it.push_back((pytype, token_string, origin))

break

if token_string in ("(", "[", "{"):

bracket_level += 1

if token_string in (")", "]", "}"):

bracket_level -= 1

if bracket_level < 0:

raise PatsyError("unmatched close bracket", origin)

pytypes.append(pytype)

token_strings.append(token_string)

origins.append(origin)

# Either we found an end_token, or we hit the end of the string

if bracket_level == 0:

expr_text = pretty_untokenize(zip(pytypes, token_strings))

if expr_text == "0":

token_type = "ZERO"

elif expr_text == "1":

token_type = "ONE"

elif _is_a(int, expr_text) or _is_a(float, expr_text):

token_type = "NUMBER"

else:

token_type = "PYTHON_EXPR"

return Token(token_type, Origin.combine(origins), extra=expr_text)

else:

raise PatsyError("unclosed bracket in embedded Python "

"expression",

Origin.combine(origins))

def _tokenize_formula(code, operator_strings):

assert "(" not in operator_strings

assert ")" not in operator_strings

magic_token_types = {"(": Token.LPAREN,

")": Token.RPAREN,

}

for operator_string in operator_strings:

magic_token_types[operator_string] = operator_string

# Once we enter a Python expression, a ( does not end it, but any other

# "magic" token does:

end_tokens = set(magic_token_types)

end_tokens.remove("(")

it = PushbackAdapter(python_tokenize(code))

for pytype, token_string, origin in it:

if token_string in magic_token_types:

yield Token(magic_token_types[token_string], origin)

else:

it.push_back((pytype, token_string, origin))

yield _read_python_expr(it, end_tokens)

def test__tokenize_formula():

code = "y ~ a + (foo(b,c + 2)) + -1 + 0 + 10"

tokens = list(_tokenize_formula(code, ["+", "-", "~"]))

expecteds = [("PYTHON_EXPR", Origin(code, 0, 1), "y"),

("~", Origin(code, 2, 3), None),

("PYTHON_EXPR", Origin(code, 4, 5), "a"),

("+", Origin(code, 6, 7), None),

(Token.LPAREN, Origin(code, 8, 9), None),

("PYTHON_EXPR", Origin(code, 9, 23), "foo(b, c + 2)"),

(Token.RPAREN, Origin(code, 23, 24), None),

("+", Origin(code, 25, 26), None),

("-", Origin(code, 27, 28), None),

("ONE", Origin(code, 28, 29), "1"),

("+", Origin(code, 30, 31), None),

("ZERO", Origin(code, 32, 33), "0"),

("+", Origin(code, 34, 35), None),

("NUMBER", Origin(code, 36, 38), "10"),

]

for got, expected in zip(tokens, expecteds):

assert isinstance(got, Token)

assert got.type == expected[0]

assert got.origin == expected[1]

assert got.extra == expected[2]

_unary_tilde = Operator("~", 1, -100)

_default_ops = [

_unary_tilde,

Operator("~", 2, -100),

Operator("+", 2, 100),

Operator("-", 2, 100),

Operator("*", 2, 200),

Operator("/", 2, 200),

Operator(":", 2, 300),

Operator("**", 2, 500),

Operator("+", 1, 100),

Operator("-", 1, 100),

]

def parse_formula(code, extra_operators=[]):

if not code.strip():

code = "~ 1"

for op in extra_operators:

if op.precedence < 0:

raise ValueError("all operators must have precedence >= 0")

operators = _default_ops + extra_operators

operator_strings = [op.token_type for op in operators]

tree = infix_parse(_tokenize_formula(code, operator_strings),

operators,

_atomic_token_types)

if not isinstance(tree, ParseNode) or tree.type != "~":

tree = ParseNode("~", None, [tree], tree.origin)

return tree

#############

_parser_tests = {

"": ["~", "1"],

" ": ["~", "1"],

" \n ": ["~", "1"],

"1": ["~", "1"],

"a": ["~", "a"],

"a ~ b": ["~", "a", "b"],

"(a ~ b)": ["~", "a", "b"],

"a ~ ((((b))))": ["~", "a", "b"],

"a ~ ((((+b))))": ["~", "a", ["+", "b"]],

"a + b + c": ["~", ["+", ["+", "a", "b"], "c"]],

"a + (b ~ c) + d": ["~", ["+", ["+", "a", ["~", "b", "c"]], "d"]],

"a + np.log(a, base=10)": ["~", ["+", "a", "np.log(a, base=10)"]],

# Note different spacing:

"a + np . log(a , base = 10)": ["~", ["+", "a", "np.log(a, base=10)"]],

# Check precedence

"a + b ~ c * d": ["~", ["+", "a", "b"], ["*", "c", "d"]],

"a + b * c": ["~", ["+", "a", ["*", "b", "c"]]],

"-a**2": ["~", ["-", ["**", "a", "2"]]],

"-a:b": ["~", ["-", [":", "a", "b"]]],

"a + b:c": ["~", ["+", "a", [":", "b", "c"]]],

"(a + b):c": ["~", [":", ["+", "a", "b"], "c"]],

"a*b:c": ["~", ["*", "a", [":", "b", "c"]]],

"a+b / c": ["~", ["+", "a", ["/", "b", "c"]]],

"~ a": ["~", "a"],

"-1": ["~", ["-", "1"]],

}

def _compare_trees(got, expected):

assert isinstance(got, ParseNode)

if got.args:

assert got.type == expected[0]

for arg, expected_arg in zip(got.args, expected[1:]):

_compare_trees(arg, expected_arg)

else:

assert got.type in _atomic_token_types

assert got.token.extra == expected

def _do_parse_test(test_cases, extra_operators):

for code, expected in six.iteritems(test_cases):

actual = parse_formula(code, extra_operators=extra_operators)

print(repr(code), repr(expected))

print(actual)

_compare_trees(actual, expected)

def test_parse_formula():

_do_parse_test(_parser_tests, [])

def test_parse_origin():

tree = parse_formula("a ~ b + c")

assert tree.origin == Origin("a ~ b + c", 0, 9)

assert tree.token.origin == Origin("a ~ b + c", 2, 3)

assert tree.args[0].origin == Origin("a ~ b + c", 0, 1)

assert tree.args[1].origin == Origin("a ~ b + c", 4, 9)

assert tree.args[1].token.origin == Origin("a ~ b + c", 6, 7)

assert tree.args[1].args[0].origin == Origin("a ~ b + c", 4, 5)

assert tree.args[1].args[1].origin == Origin("a ~ b + c", 8, 9)

# <> mark off where the error should be reported:

_parser_error_tests = [

"a <+>",

"a + <(>",

"a + b <# asdf>",

"<)>",

"a + <)>",

"<*> a",

"a + <*>",

"a + <foo[bar>",

"a + <foo{bar>",

"a + <foo(bar>",

"a + <[bar>",

"a + <{bar>",

"a + <{bar[]>",

"a + foo<]>bar",

"a + foo[]<]>bar",

"a + foo{}<}>bar",

"a + foo<)>bar",

"a + b<)>",

"(a) <.>",

"<(>a + b",

"a +< >'foo", # Not the best placement for the error

]

# Split out so it can also be used by tests of the evaluator (which also

# raises PatsyError's)

def _parsing_error_test(parse_fn, error_descs): # pragma: no cover

for error_desc in error_descs:

letters = []

start = None

end = None

for letter in error_desc:

if letter == "<":

start = len(letters)

elif letter == ">":

end = len(letters)

else:

letters.append(letter)

bad_code = "".join(letters)

assert start is not None and end is not None

print(error_desc)

print(repr(bad_code), start, end)

try:

parse_fn(bad_code)

except PatsyError as e:

print(e)

assert e.origin.code == bad_code

assert e.origin.start == start

assert e.origin.end == end

else:

assert False, "parser failed to report an error!"

def test_parse_errors(extra_operators=[]):

def parse_fn(code):

return parse_formula(code, extra_operators=extra_operators)

_parsing_error_test(parse_fn, _parser_error_tests)

_extra_op_parser_tests = {

"a | b": ["~", ["|", "a", "b"]],

"a * b|c": ["~", ["*", "a", ["|", "b", "c"]]],

}

def test_parse_extra_op():

extra_operators = [Operator("|", 2, 250)]

_do_parse_test(_parser_tests,

extra_operators=extra_operators)

_do_parse_test(_extra_op_parser_tests,

extra_operators=extra_operators)

test_parse_errors(extra_operators=extra_operators)

patsy/patsy/parse_formula.py at master · Python-Repository-Hub/patsy · GitHub

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