mypy, type hint, pep8, py27

src/pip/_internal/req/__init__.py

@@ -4,6 +4,7 @@
 from __future__ import absolute_import
 
 import logging
+from functools import partial
 
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -15,10 +16,10 @@
 try:
     from multiprocessing.pool import Pool
 except ImportError:  # Platform-specific: No multiprocessing available
-    Pool = None
+    Pool = None   # type: ignore
 
 if MYPY_CHECK_RUNNING:
-    from typing import List, Optional, Sequence
+    from typing import List, Optional, Sequence, Any
 
 __all__ = [
     "RequirementSet", "InstallRequirement",
@@ -63,16 +64,21 @@ def install_given_reqs(
         )
 
     # pre allocate installed package names
-    installed = [None] * len(to_install)
+    installed = \
+        [None] * len(to_install)  # type: List[Optional[InstallationResult]]
     install_args = [install_options, global_options, dict(
-    	root=root, home=home, prefix=prefix, warn_script_location=warn_script_location,
-    	use_user_site=use_user_site, pycompile=pycompile)]
+        root=root, home=home, prefix=prefix,
+        warn_script_location=warn_script_location,
+        use_user_site=use_user_site, pycompile=pycompile)]
 
     if Pool is not None:
         # first let's try to install in parallel, if we fail we do it by order.
         pool = Pool()
         try:
-            pool_result = pool.starmap_async(__single_install, [(install_args, r) for r in to_install])
+            pool_result = pool.map_async(partial(
+                __single_install, install_args, allow_raise=False),
+                to_install
+            )
             # python 2.7 timeout=None will not catch KeyboardInterrupt
             installed = pool_result.get(timeout=999999)
         except (KeyboardInterrupt, SystemExit):
@@ -87,12 +93,18 @@ def install_given_reqs(
     with indent_log():
         for i, requirement in enumerate(to_install):
             if installed[i] is None:
-                installed[i] = __single_install(install_args, requirement, allow_raise=True)
+                installed[i] = __single_install(
+                    install_args, requirement, allow_raise=True)
 
     return [i for i in installed if i is not None]
 
 
-def __single_install(args, a_requirement, allow_raise=False):
+def __single_install(
+        args,  # type: Sequence[Any]
+        a_requirement,  # type: InstallRequirement
+        allow_raise=False,  # type: bool
+):
+    # type: (...) -> (Optional[InstallationResult])
     if a_requirement.should_reinstall:
         logger.info('Attempting uninstall: %s', a_requirement.name)
         with indent_log():
@@ -106,20 +118,16 @@ def __single_install(args, a_requirement, allow_raise=False):
             **args[2]  # **kwargs
         )
     except Exception:
-        should_rollback = (
-                a_requirement.should_reinstall and
-                not a_requirement.install_succeeded
-        )
+        should_rollback = (a_requirement.should_reinstall and
+                           not a_requirement.install_succeeded)
         # if install did not succeed, rollback previous uninstall
         if should_rollback:
             uninstalled_pathset.rollback()
         if allow_raise:
             raise
     else:
-        should_commit = (
-                a_requirement.should_reinstall and
-                a_requirement.install_succeeded
-        )
+        should_commit = (a_requirement.should_reinstall and
+                         a_requirement.install_succeeded)
         if should_commit:
             uninstalled_pathset.commit()
         return InstallationResult(a_requirement.name)