Conditional Statements (if, elif, else)

Conditional statements allow your code to execute different actions based on certain conditions.

  • if: Checks a condition and executes a block of code if it evaluates to True.
  if condition:
    # code to execute
  • elif: Short for “else if,” checks another condition if the previous if condition was False.
  elif another_condition:
    # code to execute
  • else: Executes a block of code if none of the preceding conditions were True.
  else:
    # code to execute

Example: 

  age = 20
if age < 13:
    print("Child")
elif 13 <= age < 20:
    print("Teenager")
else:
    print("Adult")

Loops (for, while)

Loops allow you to execute a block of code repeatedly.

  • for Loop: Iterates over a sequence (e.g., a list, tuple, string).
  for item in sequence:
    # code to execute

Example: 

  for i in range(5):
    print(i)
  • while Loop: Repeats as long as a condition is True.
  while condition:
    # code to execute

Example: 

  count = 0
while count < 5:
    print(count)
    count += 1

Comprehensions (list, dictionary, and set comprehensions)

Comprehensions provide a concise way to create lists, dictionaries, and sets.

  • List Comprehensions: Create a new list by applying an expression to each item in an existing iterable.
  [expression for item in iterable]

Example: 

  squares = [x**2 for x in range(10)]
  • Dictionary Comprehensions: Create a new dictionary by applying an expression to each item in an existing iterable.
  {key_expression: value_expression for item in iterable}

Example: 

  square_dict = {x: x**2 for x in range(10)}
  • Set Comprehensions: Create a new set by applying an expression to each item in an existing iterable.
  {expression for item in iterable}

Example: 

  square_set = {x**2 for x in range(10)}

Let me know if you need further explanations or examples on any of these topics!

break, continue, and else on Loops 

  for item in items:
    if item is None:
        continue
    if item == 'STOP':
        break
    process(item)
else:
    print('Loop completed without break')

The else clause on a loop runs only if the loop was not broken out of.

enumerate and zip 

  fruits = ['apple', 'banana', 'cherry']

for index, fruit in enumerate(fruits, start=1):
    print(f"{index}. {fruit}")

names = ['Alice', 'Bob']
scores = [95, 87]
for name, score in zip(names, scores):
    print(f"{name}: {score}")

Ternary Expression 

  status = "pass" if score >= 60 else "fail"
max_val = a if a > b else b

Guard Clauses

Reduce nesting with early returns:

  def process_user(user):
    if user is None:
        return None
    if not user.is_active:
        return None
    return user.generate_report()

Practice Exercise

Write a FizzBuzz program: print numbers 1–100, but replace multiples of 3 with “Fizz”, multiples of 5 with “Buzz”, and multiples of both with “FizzBuzz”. Implement with both a for loop and a list comprehension.