Resolves #105

snippets/group_by.md

@@ -10,14 +10,11 @@ Use list comprehension to map each element to the appropriate `key`.
 
 ```py
 def group_by(lst, fn):
-  groups = {}
-  for key in list(map(fn,lst)):
-    groups[key] = [item for item in lst if fn(item) == key]
-  return groups
+    return {key : [el for el in lst if fn(el) == key] for key in map(fn,lst)}
 ```
 
 ```py
 import math
-group_by([6.1, 4.2, 6.3], math.floor); # {4: [4.2], 6: [6.1, 6.3]}
-group_by(['one', 'two', 'three'], len); # {3: ['one', 'two'], 5: ['three']}
+group_by([6.1, 4.2, 6.3], math.floor) # {4: [4.2], 6: [6.1, 6.3]}
+group_by(['one', 'two', 'three'], len) # {3: ['one', 'two'], 5: ['three']}
 ```