Today’s focus: Phase 0, Chapter 2 of Python Foundations: if/elif/else, the six comparators, and/or/not, booleans, importing modules, and the random module. Three challenges: a warm-up, an applied script, and a mini-project.

What I built

1. Even/Odd & Sign Checker (warm-up) — checks a number for even/odd and, separately, positive/negative/zero:

print(f"Welcome to Even/Odd & Sign Checker App")

# Convert input string to an integer
number = int(float(input("Enter a number: ")))

# Check if the remainder when divided by 2 is 0
if number % 2 == 0:
    print(f"{number} is Even")
else:
    print(f"{number} is Odd")

# Check the sign, independent of even/odd
if number == 0:
    print(f"{number} is a Zero number")
elif number < 0:
    print(f"{number} is a Negative Integer")
else:
    print(f"{number} is a Positive Integer")

2. Number Guessing Game (applied) — generates a secret number with random.randint(), then tells the player if they were exact, close (within 3), or far off, plus which direction to guess next:

import random

def calculate_probability(min_val, max_val):
    """Calculates the percentage chance of guessing correctly in an inclusive range [min_val, max_val]."""
    total_outcomes = (max_val - min_val) + 1
    return (1 / total_outcomes) * 100

print("Welcome to my number Guessing Game!")

min_range = 1
max_range = 10

win_percentage = calculate_probability(min_range, max_range)
print(f"Your probability of guessing correctly is {win_percentage:.1f}%\n")

guess_num = int(input(f"Guess the number from {min_range} - {max_range}: "))
secret_num = random.randint(min_range, max_range)

difference = abs(guess_num - secret_num)

if guess_num == secret_num:
    print(f"🎉 Exactly right! The secret number was {secret_num}.")
elif difference <= 3:
    if guess_num < secret_num:
        print(f"Close! You were within 3. Try guessing HIGHER next time. (Secret: {secret_num})")
    else:
        print(f"Close! You were within 3. Try guessing LOWER next time. (Secret: {secret_num})")
else:
    if guess_num < secret_num:
        print(f"Far off! Try guessing HIGHER next time. (Secret: {secret_num})")
    else:
        print(f"Far off! Try guessing LOWER next time. (Secret: {secret_num})")

3. Login Gatekeeper (mini-project) — checks a hardcoded username/password against user input with boolean logic, covering four outcomes, plus a random welcome message on success:

import random

print("Welcome to Login Gatekeeper")
welcome_msg = ("Welcome back!", "Heya there!", "Aloha amigo!")

secret_usr = "johnny123"
secret_pwd = "letmein2"

check_usr = input("Enter your username : \n")
check_pwd = input("Enter your password : \n")

if secret_usr.lower() == check_usr.lower() and secret_pwd.lower() == check_pwd.lower():
    print("You are logged in")
    print(f"{random.choice(welcome_msg)}")
elif secret_usr.lower() == check_usr.lower() and secret_pwd.lower() != check_pwd.lower():
    print("Password is incorrect")
elif secret_usr.lower() != check_usr.lower() and secret_pwd.lower() == check_pwd.lower():
    print("Username is incorrect")
else:
    print("Wrong username or password !")

Challenges I ran into

The login gatekeeper came together cleanly on the first pass — the four-outcome branching mapped naturally onto if/elif/elif/else. The other two needed a second look:

  • Reading “separately” too literally at first. My first draft of the sign checker duplicated the positive/negative/zero logic inside both the even and odd branches — technically correct, but redundant since sign doesn’t depend on even/odd at all. Pulling it out into its own independent if/elif/else block after the even/odd check cut the code in half with identical output.
  • Nested conditionals vs. combined and/or. The guessing game’s “close vs. far, higher vs. lower” logic works with nested if blocks, but the challenge was really asking for compound conditions like guess_num < secret_num and difference <= 3 chained directly. Both get the same result — nesting is just more branches to trace instead of one line to read.
  • .lower() wasn’t required but felt necessary. For the login check, comparing raw strings meant "Johnny123" would fail against "johnny123". Normalizing both sides with .lower() before comparing wasn’t in the spec, but it’s the kind of thing that matters the moment a real person types into the prompt.

What I learned

Comparators and booleans aren’t just for a single if — chaining and/or (or nesting conditionals to the same effect) is how you turn “is this true” into “is this specific combination of things true.” random.randint() and random.choice() cover two different needs: one picks a number in a range, the other picks an item from a list — useful to keep straight since they get reached for in different situations. And elif chains read better than deeply nested ifs once there are more than two or three outcomes to cover, which the login gatekeeper’s four cases made obvious.

Next

Day 3 picks up lists and loops: creating and indexing lists, .append()/.remove()/del, the in operator, for loops, range(), sum(), and break.