8th day of python challenges 111-117

venv/lib/python3.6/site-packages/isort/utils.py

@@ -0,0 +1,53 @@
+import os
+import sys
+from contextlib import contextmanager
+
+
+def exists_case_sensitive(path):
+    """
+    Returns if the given path exists and also matches the case on Windows.
+
+    When finding files that can be imported, it is important for the cases to match because while
+    file os.path.exists("module.py") and os.path.exists("MODULE.py") both return True on Windows, Python
+    can only import using the case of the real file.
+    """
+    result = os.path.exists(path)
+    if (sys.platform.startswith('win') or sys.platform == 'darwin') and result:
+        directory, basename = os.path.split(path)
+        result = basename in os.listdir(directory)
+    return result
+
+
+@contextmanager
+def chdir(path):
+    """Context manager for changing dir and restoring previous workdir after exit.
+    """
+    curdir = os.getcwd()
+    os.chdir(path)
+    try:
+        yield
+    finally:
+        os.chdir(curdir)
+
+
+def union(a, b):
+    """ Return a list of items that are in `a` or `b`
+    """
+    u = []
+    for item in a:
+        if item not in u:
+            u.append(item)
+    for item in b:
+        if item not in u:
+            u.append(item)
+    return u
+
+
+def difference(a, b):
+    """ Return a list of items from `a` that are not in `b`.
+    """
+    d = []
+    for item in a:
+        if item not in b:
+            d.append(item)
+    return d