Mention pip in Quick start.

README.md

@@ -56,7 +56,12 @@ For other Linux flavors, OS X and Windows, packages are available at
 Quick start
 -----------
 
-If you have git, first clone the mypy git repository:
+Mypy can be installed from pip:
+
+    $ pip install mypy-lang
+
+If you want to contribute and have git,
+first clone the mypy git repository:
 
     $ git clone https://github.com/JukkaL/mypy.git
 

mypy/build.py

@@ -91,7 +91,8 @@ def build(program_path: str,
           pyversion: int = 3,
           custom_typing_module: str = None,
           html_report_dir: str = None,
-          flags: List[str] = None) -> BuildResult:
+          flags: List[str] = None,
+          python_path: bool = False) -> BuildResult:
     """Build a mypy program.
 
     A single call to build performs parsing, semantic analysis and optionally
@@ -122,7 +123,7 @@ def build(program_path: str,
     data_dir = default_data_dir(bin_dir)
 
     # Determine the default module search path.
-    lib_path = default_lib_path(data_dir, target, pyversion)
+    lib_path = default_lib_path(data_dir, target, pyversion, python_path)
 
     if TEST_BUILTINS in flags:
         # Use stub builtins (to speed up test cases and to make them easier to
@@ -191,7 +192,8 @@ def default_data_dir(bin_dir: str) -> str:
         raise RuntimeError("Broken installation: can't determine base dir")
 
 
-def default_lib_path(data_dir: str, target: int, pyversion: int) -> List[str]:
+def default_lib_path(data_dir: str, target: int, pyversion: int,
+        python_path:bool) -> List[str]:
     """Return default standard library search paths."""
     # IDEA: Make this more portable.
     path = List[str]()
@@ -218,6 +220,10 @@ def default_lib_path(data_dir: str, target: int, pyversion: int) -> List[str]:
     if sys.platform != 'win32':
         path.append('/usr/local/lib/mypy')
 
+    # Contents of Python's sys.path go last, to prefer the stubs
+    if python_path:
+        path.extend(sys.path)
+
     return path
 
 

scripts/mypy

@@ -23,6 +23,7 @@ class Options:
         self.pyversion = 3
         self.custom_typing_module = None  # type: str
         self.html_report_dir = None  # type: str
+        self.python_path = False
 
 
 def main() -> None:
@@ -73,7 +74,8 @@ def type_check_only(path: str, module: str, bin_dir: str, options: Options) -> N
                 pyversion=options.pyversion,
                 custom_typing_module=options.custom_typing_module,
                 html_report_dir=options.html_report_dir,
-                flags=options.build_flags)
+                flags=options.build_flags,
+                python_path=options.python_path)
 
 
 def process_options(args: List[str]) -> Tuple[str, str, Options]:
@@ -112,6 +114,9 @@ def process_options(args: List[str]) -> Tuple[str, str, Options]:
             options.html_report_dir = args[1]
             options.build_flags.append('html-report')
             args = args[2:]
+        elif args[0] == '--use-python-path':
+            options.python_path = True
+            args = args[1:]
         else:
             usage('Unknown option: {}'.format(args[0]))
 
@@ -124,6 +129,10 @@ def process_options(args: List[str]) -> Tuple[str, str, Options]:
     if args[1:]:
         usage('Extra argument: {}'.format(args[1]))
 
+    if options.python_path and options.pyversion == 2:
+        usage('--py2 specified, '
+                'but --use-python-path will search in sys.path of Python 3')
+
     return args[0], None, options
 
 
@@ -143,6 +152,7 @@ Optional arguments:
   --html-report dir  generate a HTML report of type precision under dir/
   -m mod             type check module
   --verbose          more verbose messages
+  --use-python-path  search for modules in sys.path of running Python
 
 Environment variables:
   MYPYPATH     additional module search path