Prefer iter(dict) instead of dict.keys()

They are equivalent for iterating so remove the additional function
call.

Pattern identified as outdated by Lennart Regebro's PyCon 2017 talk
"Prehistoric Patterns in Python"

https://www.youtube.com/watch?v=V5-JH23Vk0I

4 files changed, 5 insertions, 5 deletions

diff --git a/src/flake8/main/application.py b/src/flake8/main/application.py
index d7719e3..293ac92 100644
--- a/src/flake8/main/application.py
+++ b/src/flake8/main/application.py
@@ -261,7 +261,7 @@ class Application(object):
             List of filenames to process
         """
         if self.running_against_diff:
-            files = sorted(self.parsed_diff.keys())
+            files = sorted(self.parsed_diff)
         self.file_checker_manager.start(files)
         self.file_checker_manager.run()
         LOG.info('Finished running')
diff --git a/src/flake8/main/vcs.py b/src/flake8/main/vcs.py
index 6f7499e..207d26c 100644
--- a/src/flake8/main/vcs.py
+++ b/src/flake8/main/vcs.py
@@ -36,4 +36,4 @@ def install(option, option_string, value, parser):
 
 def choices():
     """Return the list of VCS choices."""
-    return list(_INSTALLERS.keys())
+    return list(_INSTALLERS)
diff --git a/src/flake8/plugins/_trie.py b/src/flake8/plugins/_trie.py
index 4871abb..17c226f 100644
--- a/src/flake8/plugins/_trie.py
+++ b/src/flake8/plugins/_trie.py
@@ -90,7 +90,7 @@ class TrieNode(object):
         if not self.children:
             return
 
-        for prefix in sorted(self.children.keys()):
+        for prefix in sorted(self.children):
             child = self.children[prefix]
             yield child
             for child in child.traverse():
diff --git a/src/flake8/statistics.py b/src/flake8/statistics.py
index 45a7eb1..d555df2 100644
--- a/src/flake8/statistics.py
+++ b/src/flake8/statistics.py
@@ -17,7 +17,7 @@ class Statistics(object):
         :rtype:
             list(str)
         """
-        return sorted({key.code for key in self._store.keys()})
+        return sorted({key.code for key in self._store})
 
     def record(self, error):
         """Add the fact that the error was seen in the file.
@@ -55,7 +55,7 @@ class Statistics(object):
         :returns:
             Generator of instances of :class:`Statistic`
         """
-        matching_errors = sorted(key for key in self._store.keys()
+        matching_errors = sorted(key for key in self._store
                                  if key.matches(prefix, filename))
         for error_code in matching_errors:
             yield self._store[error_code]