do not use 'l' as a variable name, to appease new flake8 version

- new E741 flake8 checks disallow 'l', 'O', and 'I' as variable names

- rework parts of the code that use this, to be compliant

- we could add exceptions for this, but we're trying to mostly keep up
  with PEP8 and we already have more than a few exceptions.

8 files changed, 53 insertions, 55 deletions

diff --git a/lib/spack/spack/build_environment.py b/lib/spack/spack/build_environment.py
index aac1d38f5a..46bae86712 100644
--- a/lib/spack/spack/build_environment.py
+++ b/lib/spack/spack/build_environment.py
@@ -677,11 +677,11 @@ def get_package_context(traceback, context=3):
     # Build a message showing context in the install method.
     sourcelines, start = inspect.getsourcelines(frame)
 
-    l = frame.f_lineno - start
-    start_ctx = max(0, l - context)
-    sourcelines = sourcelines[start_ctx:l + context + 1]
+    fl = frame.f_lineno - start
+    start_ctx = max(0, fl - context)
+    sourcelines = sourcelines[start_ctx:fl + context + 1]
     for i, line in enumerate(sourcelines):
-        is_error = start_ctx + i == l
+        is_error = start_ctx + i == fl
         mark = ">> " if is_error else "   "
         marked = "  %s%-6d%s" % (mark, start_ctx + i, line.rstrip())
         if is_error:
diff --git a/lib/spack/spack/cmd/info.py b/lib/spack/spack/cmd/info.py
index 0a54990b14..08d47a98db 100644
--- a/lib/spack/spack/cmd/info.py
+++ b/lib/spack/spack/cmd/info.py
@@ -189,12 +189,10 @@ def print_text_info(pkg):
         # Here we sort first on the fact that a version is marked
         # as preferred in the package, then on the fact that the
         # version is not develop, then lexicographically
-        l = [
-            (value.get('preferred', False), not key.isdevelop(), key)
-            for key, value in pkg.versions.items()
-        ]
-        l = sorted(l)
-        _, _, preferred = l.pop()
+        key_fn = lambda v: (pkg.versions[v].get('preferred', False),
+                            not v.isdevelop(),
+                            v)
+        preferred = sorted(pkg.versions, key=key_fn).pop()
 
         f = fs.for_package_version(pkg, preferred)
         line = version('    {0}'.format(pad(preferred))) + str(f)
diff --git a/lib/spack/spack/modules/common.py b/lib/spack/spack/modules/common.py
index 3907e5e654..f984c78561 100644
--- a/lib/spack/spack/modules/common.py
+++ b/lib/spack/spack/modules/common.py
@@ -154,13 +154,13 @@ def dependencies(spec, request='all'):
     # FIXME : step among nodes that refer to the same package?
     seen = set()
     seen_add = seen.add
-    l = sorted(
+    deps = sorted(
         spec.traverse(order='post',
                       cover='nodes',
                       deptype=('link', 'run'),
                       root=False),
         reverse=True)
-    return [x for x in l if not (x in seen or seen_add(x))]
+    return [d for d in deps if not (d in seen or seen_add(d))]
 
 
 def merge_config_rules(configuration, spec):
@@ -204,8 +204,8 @@ def merge_config_rules(configuration, spec):
 
     # Which instead we want to mark as prerequisites
     prerequisite_strategy = spec_configuration.get('prerequisites', 'none')
-    l = dependencies(spec, prerequisite_strategy)
-    spec_configuration['prerequisites'] = l
+    spec_configuration['prerequisites'] = dependencies(
+        spec, prerequisite_strategy)
 
     # Attach options that are spec-independent to the spec-specific
     # configuration
@@ -274,7 +274,7 @@ class BaseConfiguration(object):
         """List of environment modifications that should be done in the
         module.
         """
-        l = spack.environment.EnvironmentModifications()
+        env_mods = spack.environment.EnvironmentModifications()
         actions = self.conf.get('environment', {})
 
         def process_arglist(arglist):
@@ -287,9 +287,9 @@ class BaseConfiguration(object):
 
         for method, arglist in actions.items():
             for args in process_arglist(arglist):
-                getattr(l, method)(*args)
+                getattr(env_mods, method)(*args)
 
-        return l
+        return env_mods
 
     @property
     def suffixes(self):
@@ -379,12 +379,12 @@ class BaseConfiguration(object):
         return self.conf.get('filter', {}).get('environment_blacklist', {})
 
     def _create_list_for(self, what):
-        l = []
+        whitelist = []
         for item in self.conf[what]:
             conf = type(self)(item)
             if not conf.blacklisted:
-                l.append(item)
-        return l
+                whitelist.append(item)
+        return whitelist
 
     @property
     def verbose(self):
@@ -592,8 +592,8 @@ class BaseContext(tengine.Context):
 
     def _create_module_list_of(self, what):
         m = self.conf.module
-        l = getattr(self.conf, what)
-        return [m.make_layout(x).use_name for x in l]
+        return [m.make_layout(x).use_name
+                for x in getattr(self.conf, what)]
 
     @tengine.context_property
     def verbose(self):
diff --git a/lib/spack/spack/modules/lmod.py b/lib/spack/spack/modules/lmod.py
index 34e968c1f1..d09bd679fd 100644
--- a/lib/spack/spack/modules/lmod.py
+++ b/lib/spack/spack/modules/lmod.py
@@ -255,10 +255,9 @@ class LmodFileLayout(BaseFileLayout):
         available = self.conf.available
         # List of services that are part of the hierarchy
         hierarchy = self.conf.hierarchy_tokens
-        # List of items that are both in the hierarchy and available
-        l = [x for x in hierarchy if x in available]
-        # Tokenize each part
-        parts = [self.token_to_path(x, available[x]) for x in l]
+        # Tokenize each part that is both in the hierarchy and available
+        parts = [self.token_to_path(x, available[x])
+                 for x in hierarchy if x in available]
         return parts
 
     @property
@@ -296,9 +295,9 @@ class LmodFileLayout(BaseFileLayout):
         for item in to_be_processed:
             hierarchy = self.conf.hierarchy_tokens
             available = self.conf.available
-            l = [x for x in hierarchy if x in item]
-            available_combination.append(tuple(l))
-            parts = [self.token_to_path(x, available[x]) for x in l]
+            ac = [x for x in hierarchy if x in item]
+            available_combination.append(tuple(ac))
+            parts = [self.token_to_path(x, available[x]) for x in ac]
             unlocked[None].append(tuple([self.arch_dirname] + parts))
 
         # Deduplicate the list
@@ -319,9 +318,10 @@ class LmodFileLayout(BaseFileLayout):
                 hierarchy = self.conf.hierarchy_tokens
                 available = self.conf.available
                 token2path = lambda x: self.token_to_path(x, available[x])
-                l = [x for x in hierarchy if x in item]
                 parts = []
-                for x in l:
+                for x in hierarchy:
+                    if x not in item:
+                        continue
                     value = token2path(x) if x in available else x
                     parts.append(value)
                 unlocked[m].append(tuple([self.arch_dirname] + parts))
@@ -374,17 +374,17 @@ class LmodContext(BaseContext):
     @tengine.context_property
     def unlocked_paths(self):
         """Returns the list of paths that are unlocked unconditionally."""
-        l = make_layout(self.spec)
-        return [os.path.join(*parts) for parts in l.unlocked_paths[None]]
+        layout = make_layout(self.spec)
+        return [os.path.join(*parts) for parts in layout.unlocked_paths[None]]
 
     @tengine.context_property
     def conditionally_unlocked_paths(self):
         """Returns the list of paths that are unlocked conditionally.
         Each item in the list is a tuple with the structure (condition, path).
         """
-        l = make_layout(self.spec)
+        layout = make_layout(self.spec)
         value = []
-        conditional_paths = l.unlocked_paths
+        conditional_paths = layout.unlocked_paths
         conditional_paths.pop(None)
         for services_needed, list_of_path_parts in conditional_paths.items():
             condition = ' and '.join([x + '_name' for x in services_needed])
diff --git a/lib/spack/spack/modules/tcl.py b/lib/spack/spack/modules/tcl.py
index 038fe91473..345667e99d 100644
--- a/lib/spack/spack/modules/tcl.py
+++ b/lib/spack/spack/modules/tcl.py
@@ -86,7 +86,7 @@ class TclContext(BaseContext):
     @tengine.context_property
     def conflicts(self):
         """List of conflicts for the tcl module file."""
-        l = []
+        fmts = []
         naming_scheme = self.conf.naming_scheme
         f = string.Formatter()
         for item in self.conf.conflicts:
@@ -106,9 +106,9 @@ class TclContext(BaseContext):
                                                  cformat=item))
                         raise SystemExit('Module generation aborted.')
                 item = self.spec.format(item)
-            l.append(item)
+            fmts.append(item)
         # Substitute spec tokens if present
-        return [self.spec.format(x) for x in l]
+        return [self.spec.format(x) for x in fmts]
 
 
 class TclModulefileWriter(BaseModuleFileWriter):
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 3a4a5953b2..2d097bc739 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -1844,8 +1844,8 @@ class Spec(object):
                 )
                 mvar.value = mvar.value + tuple(patches)
                 # FIXME: Monkey patches mvar to store patches order
-                l = getattr(mvar, '_patches_in_order_of_appearance', [])
-                mvar._patches_in_order_of_appearance = dedupe(l + patches)
+                p = getattr(mvar, '_patches_in_order_of_appearance', [])
+                mvar._patches_in_order_of_appearance = dedupe(p + patches)
 
         for s in self.traverse():
             if s.external_module:
diff --git a/lib/spack/spack/test/llnl/util/file_list.py b/lib/spack/spack/test/llnl/util/file_list.py
index 4b71881313..7761176cdc 100644
--- a/lib/spack/spack/test/llnl/util/file_list.py
+++ b/lib/spack/spack/test/llnl/util/file_list.py
@@ -37,7 +37,7 @@ from llnl.util.filesystem import find_libraries, find_headers
 def library_list():
     """Returns an instance of LibraryList."""
     # Test all valid extensions: ['.a', '.dylib', '.so']
-    l = [
+    libs = [
         '/dir1/liblapack.a',
         '/dir2/libpython3.6.dylib',  # name may contain periods
         '/dir1/libblas.a',
@@ -45,21 +45,21 @@ def library_list():
         'libmpi.so.20.10.1',  # shared object libraries may be versioned
     ]
 
-    return LibraryList(l)
+    return LibraryList(libs)
 
 
 @pytest.fixture()
 def header_list():
     """Returns an instance of header list"""
     # Test all valid extensions: ['.h', '.hpp', '.hh', '.cuh']
-    h = [
+    headers = [
         '/dir1/Python.h',
         '/dir2/date.time.h',
         '/dir1/pyconfig.hpp',
         '/dir3/core.hh',
         'pymem.cuh',
     ]
-    h = HeaderList(h)
+    h = HeaderList(headers)
     h.add_macro('-DBOOST_LIB_NAME=boost_regex')
     h.add_macro('-DBOOST_DYN_LINK')
     return h
@@ -129,11 +129,11 @@ class TestLibraryList(object):
             '/dir4/libnew.a'
         ]
         another = LibraryList(pylist)
-        l = library_list + another
-        assert len(l) == 7
+        both = library_list + another
+        assert len(both) == 7
 
-        # Invariant : l == l + l
-        assert l == l + l
+        # Invariant
+        assert both == both + both
 
         # Always produce an instance of LibraryList
         assert type(library_list + pylist) == type(library_list)
@@ -258,7 +258,7 @@ def test_searching_order(search_fn, search_list, root, kwargs):
     # Now reverse the result and start discarding things
     # as soon as you have matches. In the end the list should
     # be emptied.
-    l = list(reversed(result))
+    L = list(reversed(result))
 
     # At this point make sure the search list is a sequence
     if isinstance(search_list, six.string_types):
@@ -267,11 +267,11 @@ def test_searching_order(search_fn, search_list, root, kwargs):
     # Discard entries in the order they appear in search list
     for x in search_list:
         try:
-            while fnmatch.fnmatch(l[-1], x) or x in l[-1]:
-                l.pop()
+            while fnmatch.fnmatch(L[-1], x) or x in L[-1]:
+                L.pop()
         except IndexError:
             # List is empty
             pass
 
     # List should be empty here
-    assert len(l) == 0
+    assert len(L) == 0
diff --git a/lib/spack/spack/util/web.py b/lib/spack/spack/util/web.py
index a1944b8d65..92e9a3d48e 100644
--- a/lib/spack/spack/util/web.py
+++ b/lib/spack/spack/util/web.py
@@ -285,9 +285,9 @@ def find_versions_of_archive(archive_urls, list_url=None, list_depth=0):
     pages = {}
     links = set()
     for lurl in list_urls:
-        p, l = spider(lurl, depth=list_depth)
-        pages.update(p)
-        links.update(l)
+        pg, lnk = spider(lurl, depth=list_depth)
+        pages.update(pg)
+        links.update(lnk)
 
     # Scrape them for archive URLs
     regexes = []