Update Python_walkthrough.ipynb

Author: marcoalopez

notebooks/Python_walkthrough.ipynb

@@ -1102,7 +1102,7 @@
     "\n",
     "## Lists\n",
     "\n",
-    "Python **lists** are ordered sequences of values of any type where each value is identified by an index. The different elements need not be of the same type. A key concept is that elements in a **list are mutable** (i.e. their values or size can be modified after creation). A list is constructed using square brackets."
+    "Python **lists** are ordered sequences of values of any type where each value is identified by an index. The different elements need not be of the same type. A key concept is that elements in a **list are mutable** (i.e. their values or size can be modified after creation). A list is constructed using brackets."
    ]
   },
   {
@@ -1473,7 +1473,7 @@
    "source": [
     "## Dictionaries\n",
     "\n",
-    "A _dictionary_ is a structured type used to store _key-value_ pairs. This is a very versatile structure as the values can be of any type supported by Python (e.g. integers, scalars, lists, numpy arrays, etc.). Dictionaries are constructed with curly brackets and key and values are separated by a colon as follows"
+    "A _dictionary_ is a structured type used to store _key-value_ pairs. This is a very versatile structure as the values can be of any type supported by Python (e.g. integers, scalars, lists, numpy arrays, etc.). Dictionaries are constructed with curly braces and key and values are separated by a colon as follows"
    ]
   },
   {