variable naming of loops and contexts

Author: Sagar Chalise

docs/python/variables.md

@@ -14,3 +14,6 @@ sidebar_label: Variables
     - `__{variable_name}` are not directly accesible while `_{variable_name}` are. They are just for convention.
 * Avoid builtin variable clash. Especially in `globals`. You can attach `_` as suffix to builtin names if you deem the name necessary for your variable.
     - `all` or `id` is very tempting variable names but they are builtin methods in python. Go with `all_` or `id_` for these or better yet choose something else as a name.
+* While it is tempting to use `i`, `k`, `v` and `f` especially in contexts and for loops. Please avoid them.
+    - use `key`, `value`, `index` instead.
+    - use descriptive contexts such as `with open(FILENAME) as open_file: pass` rather that `with open(FILENAME) as f:`