Expose read, read_str, and eval in Python

- Expose `read`, `read_str`, and `eval` in Python
- Add string evaluation example to interop section of docs
- Add test for `eval`
- Explain `eof` keyword argument in `read` docstring

NEWS

@@ -27,6 +27,10 @@ Changes from 0.13.0
    * `exec` now works under Python 2
    * No TypeError from multi-arity defn returning values evaluating to None
 
+   [ Misc. Improvements ]
+   * `read`, `read_str`, and `eval` are exposed and documented as top-level
+     functions in the `hy` module
+
 Changes from 0.12.1
 
    [ Language Changes ]

docs/language/interop.rst

@@ -131,5 +131,17 @@ argument::
     test()
     bar
 
+Evaluating strings of Hy code from Python
+-----------------------------------------
 
+Evaluating a string (or ``file`` object) containing a Hy expression requires
+two separate steps. First, use the ``read_str`` function (or ``read`` for a
+``file`` object) to turn the expression into a Hy model::
 
+    >>> import hy
+    >>> expr = hy.read_str("(- (/ (+ 1 3 88) 2) 8)")
+
+Then, use the ``eval`` function to evaluate it::
+
+    >>> hy.eval(expr)
+    38.0

hy/__init__.py

@@ -10,3 +10,7 @@ from hy.models import HyExpression, HyInteger, HyKeyword, HyComplex, HyString, H
 
 import hy.importer  # NOQA
 # we import for side-effects.
+
+
+from hy.core.language import read, read_str  # NOQA
+from hy.importer import hy_eval as eval  # NOQA

hy/core/language.hy

@@ -426,8 +426,8 @@
 
 (defn read [&optional [from-file sys.stdin]
                       [eof ""]]
-  "Read from input and returns a tokenized string.
-   Can take a given input buffer to read from"
+  "Read from input and returns a tokenized string. Can take a given input buffer
+   to read from, and a single byte as EOF (defaults to an empty string)"
   (setv buff "")
   (while True
     (setv inn (string (.readline from-file)))

tests/importer/test_importer.py

@@ -2,12 +2,14 @@
 # This file is part of Hy, which is free software licensed under the Expat
 # license. See the LICENSE.
 
+import hy
 from hy.importer import (import_file_to_module, import_buffer_to_ast,
                          MetaLoader, get_bytecode_path)
 from hy.errors import HyTypeError
 import os
 import ast
 import tempfile
+from fractions import Fraction
 
 
 def test_basics():
@@ -64,3 +66,20 @@ def test_import_autocompiles():
 
     os.remove(f.name)
     os.remove(get_bytecode_path(f.name))
+
+
+def test_eval():
+    def eval_str(s):
+        return hy.eval(hy.read_str(s))
+
+    assert eval_str('[1 2 3]') == [1, 2, 3]
+    assert eval_str('{"dog" "bark" "cat" "meow"}') == {
+        'dog': 'bark', 'cat': 'meow'}
+    assert eval_str('(, 1 2 3)') == (1, 2, 3)
+    assert eval_str('#{3 1 2}') == {1, 2, 3}
+    assert eval_str('1/2') == Fraction(1, 2)
+    assert eval_str('(.strip " fooooo   ")') == 'fooooo'
+    assert eval_str(
+        '(if True "this is if true" "this is if false")') == "this is if true"
+    assert eval_str('(list-comp (pow num 2) (num (range 100)) (= (% num 2) 1))') == [
+        pow(num, 2) for num in range(100) if num % 2 == 1]