Add operators and conditionals

Author: Sahil

day2/conditionals.py

@@ -0,0 +1,47 @@
+'''
+This program checks if a message is rude or polite
+A message is rude if the parameter x is less than 1 or greater than 10
+'''
+
+x = int(input())
+
+if (x < 1):
+  print("Rude message")
+
+if (x > 10):
+  print("Rude message")
+
+'''
+The problem with the above code is redundancy!
+A principal rule of programming is to never ever have 
+two pieces of code to do the same thing.
+It can be improved as shown below:
+'''
+if (x < 1 or x > 10):
+  print("Rude message")
+
+if (x >= 1 and x <= 10):
+  print("Polite message")
+
+'''
+The problem with above code is robustness
+what if the condition of rudeness changes and we will have to
+rewrite both the conditions above,
+we can simplify it using an else construct :)
+'''
+
+if (x < 1 or x > 10):
+  print("Rude message")
+else:
+  print("Polite message")
+
+# if elif
+# say if only x < 1 are rude messages
+# from 1 to 10 are polite messages
+# and after 10 are other types!
+if (x < 1):
+  print("Rude messsage")
+elif (x >= 1 and x <= 10):
+  print("Polite message")
+else:
+  print("Any other message")

day2/operators.py

@@ -0,0 +1,19 @@
+# comparison operators
+a = 3
+less_than_3 = a < 3
+print(less_than_3) # False
+print(type(less_than_3)) # <class 'bool'>
+
+# other relational operators: >, >=, ==, !=
+print(a == 3) # True
+print(a != 3) # False
+
+# logical operators: or, and, not
+x = 5
+res_one = x < 1 or x > 10
+res_two = x >= 1 and x <= 10
+print(res_one) # False
+print(res_two) # True
+
+user_logged_in = True
+print(not user_logged_in)

lecture2.md

@@ -4,15 +4,31 @@
 [Basics of Python](day2/recap.py)
 
 ## Operators
+[Code](day2/operators.py)
+
+### Relational Operators
+- comparison operators (<, >, <=, >=)
+- Equals (==)
+- Not equals (!=)
+
+### Logical Operators
 - and
 - or
 - not
-- comparisons (<, >, ==, !=)
 
 ## Conditionals
-- if
-- else
-- elif
+[Code](day2/conditionals.py)
+
+- Decision making statements in programming languages decide the direction of flow of program execution.
+
+- There comes situations in real life when we need to make some decisions and based on these decisions, we decide what should we do next. 
+
+- Similar situations arise in programming also where we need to make some decisions and based on these decision we will execute the next block of code.
+
+- Majorly, the following 3 conditional constructs are used in Python:
+    - if
+    - else
+    - elif
 
 ## Loops
 - for