Week 2: Strings in Depth, Decisions (if/elif/else) and Loops

Month 1 | Main goal: The student can process text, make decisions with if, and repeat work with while/for — and build the "Bahatisha Namba" (Guess the Number) game.

Teacher Preparation (read before the week starts)

• There is nothing new to install. Create the folder python_darasa\wiki02.
• Read: https://docs.python.org/3/tutorial/introduction.html#text (strings) and https://docs.python.org/3/tutorial/controlflow.html (if, for, range, break, continue).
• Practise yourself: write the "Bahatisha Namba" game (Session 3) on your own before Session 3. If you can write it without looking, you will teach it with confidence.
• The most important thing this week: INDENTATION. Python uses 4 spaces at the start of a line to show code that is "inside" an if, while or for. VS Code inserts 4 spaces when you press Tab. Make sure the bottom right corner of VS Code says "Spaces: 4".
• Know how to stop a stuck program (an infinite loop): press Ctrl + C in the terminal. You will need it!

Week Goals (by the end of the week the student will be able to...)

1. Use indexing (s[0], s[-1]) and slicing (s[1:4], s[::-1]) on strings.
2. Use string methods: upper, lower, title, strip, replace, split, find, count, startswith, isdigit, as well as len() and in.
3. Use f-strings: f"Habari {jina}", f"{bei:,.2f}".
4. Write decisions with if / elif / else and nested conditions.
5. Repeat work with while and for, and use range(), break, continue.
6. Use random.randint() to build a number-guessing game.

Session 1 — Strings in Depth: indexing, slicing, methods, f-strings

Session flow

1. Homework review (kibadilishaji.py)
2. A string is a sequence of characters: len(), indexing, negative index
3. Slicing [start:stop:step]
4. Break
5. String methods
6. f-strings and number formatting
7. In-class exercise
8. Q&A + homework

Explanation for the teacher (read this first)

• A string is a sequence of characters. Each character has a position number called an index, and the index starts at 0, not 1.

  text

  Copy

   T   a   n   z   a   n   i   a
   0   1   2   3   4   5   6   7
  -8  -7  -6  -5  -4  -3  -2  -1
  

• s[0] → the first character; s[-1] → the last character. len(s) → the number of characters (8). An index greater than len(s)-1 → IndexError.

• Slicing s[start:stop] takes from start up to but not including stop. s[0:3] → "Tan". Leave out start → from the beginning; leave out stop → to the end. s[::2] → every second character. s[::-1] → the reversed string.
• Slicing doesn't raise IndexError even if you go too far: s[0:100] → the whole string.
• Strings cannot be changed (immutable): s[0] = "t" → TypeError. Methods don't change the original string; they return a new string. That's why we write jina = jina.upper().
• Important methods: .upper(), .lower(), .title(), .capitalize(), .strip() (removes spaces at the edges), .replace(a, b), .split() (splits into a list — we will see more of it in Week 3), .find(x) (the index or -1), .count(x), .startswith(x), .endswith(x), .isdigit(), .isalpha(). "x" in s → True/False.
• f-string: put f before the quote, then put variables inside {}: f"Jina: {jina}, umri: {umri}". You can include calculations: f"{a + b}". Formatting: {x:.2f} → 2 decimals; {x:,} → thousands commas; {x:,.2f} → both; {jina:>10} → align right in width 10; {jina:<10} left; {jina:^10} centre.

Say this to the student

• "A string is like a train with carriages. Each carriage holds one character, and the carriages are numbered starting from 0. You can call the last carriage -1."
• "Slicing is like cutting a piece of bread: [2:5] means 'start cutting at mark 2, stop before mark 5'."
• "A string cannot be changed — it is like words carved into stone. If you want something different, you carve a new stone."
• "An f-string is like a form with blank spaces {} — Python fills those spaces with the values of variables."

Type this code live (share screen)

Step 1 — strings.py: indexing and len

nchi = "Tanzania"
print(len(nchi))      # 8
print(nchi[0])        # T
print(nchi[1])        # a
print(nchi[-1])       # a
print(nchi[-2])       # i
print(nchi[len(nchi) - 1])   # a  (herufi ya mwisho kwa njia ndefu)

Step 2 — Slicing

nchi = "Tanzania"
print(nchi[0:3])      # Tan
print(nchi[3:])       # zania
print(nchi[:5])       # Tanza
print(nchi[-3:])      # nia
print(nchi[::2])      # Tnai
print(nchi[::-1])     # ainaznaT
print(nchi[0:100])    # Tanzania (hakuna error)

Step 3 — Methods

ujumbe = "   habari ya asubuhi, mwalimu   "
print(ujumbe.strip())               # habari ya asubuhi, mwalimu
print(ujumbe.strip().upper())       # HABARI YA ASUBUHI, MWALIMU
print(ujumbe.strip().title())       # Habari Ya Asubuhi, Mwalimu
print(ujumbe.replace("asubuhi", "jioni").strip())   # habari ya jioni, mwalimu
print(ujumbe.count("a"))            # 5
print(ujumbe.find("mwalimu"))       # 22
print(ujumbe.find("Dodoma"))        # -1 (haipo)
print("habari" in ujumbe)           # True
print(ujumbe)                       # haijabadilika! bado ina nafasi

Emphasise the last line: methods don't change the original string.

simu = "0712345678"
print(simu.isdigit())          # True
print(simu.startswith("07"))   # True
print("Amina".isalpha())       # True
print("Amina 2".isalpha())     # False (nafasi na namba)

sentensi = "Python ni rahisi sana"
maneno = sentensi.split()
print(maneno)          # ['Python', 'ni', 'rahisi', 'sana']
print(len(maneno))     # 4

Step 4 — f-strings

jina = "Juma"
umri = 22
bei = 1234567.891

print(f"Jina langu ni {jina} na nina miaka {umri}.")
print(f"Mwaka ujao: {umri + 1}")
print(f"Jina kwa herufi kubwa: {jina.upper()}")
print(f"Bei: {bei:.2f}")
print(f"Bei: {bei:,.2f} TZS")
print(f"[{jina:<10}]")
print(f"[{jina:>10}]")
print(f"[{jina:^10}]")

Output:

Jina langu ni Juma na nina miaka 22.
Mwaka ujao: 23
Jina kwa herufi kubwa: JUMA
Bei: 1234567.89
Bei: 1,234,567.89 TZS
[Juma      ]
[      Juma]
[   Juma   ]

Step 5 — Real example: cleaning up a user's name

jina = input("Andika jina lako: ")
jina_safi = jina.strip().title()
print(f"Karibu {jina_safi}! Jina lako lina herufi {len(jina_safi)}.")
print(f"Herufi ya kwanza: {jina_safi[0]}, ya mwisho: {jina_safi[-1]}")
print(f"Jina lako kinyume: {jina_safi[::-1]}")

Andika jina lako:    neema
Karibu Neema! Jina lako lina herufi 5.
Herufi ya kwanza: N, ya mwisho: a
Jina lako kinyume: ameeN

Questions to ask the student

1. "Python"[2]? — Answer: "t".
2. "Python"[-1]? — Answer: "n".
3. "Python"[1:4]? — Answer: "yth" (index 1, 2, 3).
4. After s = "abc"; s.upper(), what is s? — Answer: still "abc"; you must write s = s.upper().
5. How would you reverse a string? — Answer: s[::-1].
6. "ana" in "Tanzania"? — Answer: False. T-a-n-z-a-n-i-a contains "an" but there is no "a-n-a" in a row. "zan" in "Tanzania" is True. Confirm it together in the REPL.

Common mistakes

In-class exercise

1. Ask for a full name (e.g. "amina juma hassan"). Display: the name with title(), the initials (A.J.H.), and the number of letters without spaces.
2. Ask for a word; display whether it is a palindrome (reads the same backwards, e.g. "kayak", "ada") — True/False.
3. Ask for a phone number; display True if it has 10 characters, all digits, and starts with "0".

# zoezi 1
jina = input("Jina kamili: ").strip()
maneno = jina.title().split()
print("Jina:", jina.title())
initials = maneno[0][0] + "." + maneno[1][0] + "." + maneno[2][0] + "."
print("Initials:", initials)
print("Herufi bila nafasi:", len(jina.replace(" ", "")))
# Kumbuka: hii inafanya kazi kwa majina 3 tu; Wiki 2 Kipindi 3 (for loop) tutaifanya ya jumla.

# zoezi 2
neno = input("Neno: ").strip().lower()
print("Ni palindrome?", neno == neno[::-1])

# zoezi 3
simu = input("Namba ya simu: ").strip()
sahihi = len(simu) == 10 and simu.isdigit() and simu.startswith("0")
print("Namba sahihi?", sahihi)

Session 2 — Decisions: if / elif / else and Nested Conditions

Session flow

1. Homework review
2. if alone, indentation, else
3. elif — multiple choices (example: grade bands for marks)
4. Break
5. Nested conditions + combining with and/or
6. Big example: transport fare calculator / simple ATM
7. In-class exercise
8. Q&A + homework

Explanation for the teacher (read this first)

• if sharti: (sharti = condition) — if the condition is True, Python runs the indented lines below it. If it is False, it skips them.

• Structure:

  python

  Copy

  if sharti_1:
      # inafanyika kama sharti_1 ni True
  elif sharti_2:
      # inafanyika kama sharti_1 ni False NA sharti_2 ni True
  else:
      # inafanyika kama yote juu ni False
  

• Key points: a colon : at the end of if/elif/else; 4-space indentation; elif and else are optional; Python checks from top to bottom and stops at the first condition that is True — so order matters (marks ≥ 80 must be checked before ≥ 60).

• Nested if = an if inside an if (double indentation = 8 spaces).
• Truthiness: if jina: is True if jina is not an empty string. if 0: is False.
• String comparison is case-sensitive: use .lower() on user input: if jibu.lower() == "ndiyo":.
• Ternary (briefly, no need to teach it in depth): hali = "mtu mzima" if umri >= 18 else "mtoto".

Say this to the student

• "if is like a crossroads. When you get there, you look at the sign: 'if it is raining, take an umbrella; otherwise (else), wear a sun hat'."
• "elif is like a door guard going through a list in order: 'Do you have a VIP card? Enter door A. No? Do you have a regular ticket? Door B. No? You can't come in (else).' Once the guard gets the first answer, the others aren't checked."
• "Indentation is like indented paragraphs in a notebook — the lines moved inward 'belong' to the if above them."

Type this code live (share screen)

Step 1 — if and else (maamuzi.py, decisions)

umri = int(input("Umri wako: "))

if umri >= 18:
    print("Wewe ni mtu mzima.")
    print("Unaweza kupiga kura.")
else:
    print("Bado wewe ni mtoto.")
    print(f"Subiri miaka {18 - umri} zaidi.")

print("Asante!")    # huu uko nje ya if — unafanyika kila mara

Run it twice (age 25, then 15):

Umri wako: 25
Wewe ni mtu mzima.
Unaweza kupiga kura.
Asante!

Umri wako: 15
Bado wewe ni mtoto.
Subiri miaka 3 zaidi.
Asante!

Step 2 — elif: grade bands for marks (the NECTA system, simplified)

alama = int(input("Alama (0-100): "))

if alama < 0 or alama > 100:
    print("Alama si sahihi!")
elif alama >= 75:
    print("Daraja: A")
elif alama >= 65:
    print("Daraja: B")
elif alama >= 45:
    print("Daraja: C")
elif alama >= 30:
    print("Daraja: D")
else:
    print("Daraja: F")

Ask: "A mark of 80 is also >= 65. Why doesn't it show B?" → Because Python stops at the first condition that is True (>= 75).

Show the wrong order:

alama = 80
if alama >= 30:
    print("D")      # inasimama hapa! si sahihi
elif alama >= 75:
    print("A")

Step 3 — Nested if

ana_tiketi = input("Una tiketi? (ndiyo/hapana): ").strip().lower()

if ana_tiketi == "ndiyo":
    umri = int(input("Umri: "))
    if umri >= 18:
        print("Karibu kwenye tamasha!")
    else:
        print("Samahani, tamasha ni la watu wazima tu.")
else:
    print("Nunua tiketi kwanza.")

Step 4 — Combining and/or instead of nesting

siku = input("Leo ni siku gani? ").strip().lower()

if siku == "jumamosi" or siku == "jumapili":
    print("Ni wikendi! Pumzika.")
else:
    print("Ni siku ya kazi/shule.")

Step 5 — Big example: simple ATM (atm.py)

salio = 150000
PIN_SAHIHI = "1234"

pin = input("Weka PIN: ")
if pin != PIN_SAHIHI:
    print("PIN si sahihi. Kadi imezuiliwa.")
else:
    print("1. Angalia salio")
    print("2. Toa pesa")
    chaguo = input("Chagua (1/2): ")

    if chaguo == "1":
        print(f"Salio lako ni {salio:,} TZS")
    elif chaguo == "2":
        kiasi = int(input("Kiasi cha kutoa: "))
        if kiasi <= 0:
            print("Kiasi si sahihi.")
        elif kiasi > salio:
            print("Salio halitoshi.")
        elif kiasi % 1000 != 0:
            print("ATM inatoa noti za 1,000 na kuendelea tu.")
        else:
            salio -= kiasi
            print(f"Chukua pesa zako. Salio jipya: {salio:,} TZS")
    else:
        print("Chaguo si sahihi.")

Example:

Weka PIN: 1234
1. Angalia salio
2. Toa pesa
Chagua (1/2): 2
Kiasi cha kutoa: 50000
Chukua pesa zako. Salio jipya: 100,000 TZS

Questions to ask the student

1. Why do we put : at the end of an if? — Answer: It is a Python rule; it shows that a block is starting.
2. How many elifs can an if have? — Answer: Any number; only one else, and it comes last.
3. If x = 0, what will if x: do? — Answer: It skips the block, because 0 is "falsy".
4. Why do we use .lower() on the user's answer? — Answer: So that "Ndiyo", "NDIYO" and "ndiyo" (yes) are all accepted.
5. The difference between two if...ifs and if...elif? — Answer: Two ifs are both checked; elif is checked only if the first was False.

Common mistakes

In-class exercise

1. Ask for a number; say whether it is positive, negative or zero, and whether it is even or odd.
2. Ask for three numbers; display the largest (without using max()).
3. Transport fare: ask for the distance (km) and whether the passenger is a student. Fare = 500 TZS per km for the first 10 km, 300 for each km after that. Students get a 50% discount.

# zoezi 1
n = int(input("Namba: "))
if n > 0:
    print("Chanya")
elif n < 0:
    print("Hasi")
else:
    print("Sifuri")

if n % 2 == 0:
    print("Shufwa")
else:
    print("Witiri")

# zoezi 2
a = float(input("a: "))
b = float(input("b: "))
c = float(input("c: "))
if a >= b and a >= c:
    kubwa = a
elif b >= a and b >= c:
    kubwa = b
else:
    kubwa = c
print("Kubwa zaidi:", kubwa)

# zoezi 3
km = float(input("Umbali (km): "))
mwanafunzi = input("Mwanafunzi? (ndiyo/hapana): ").strip().lower()

if km <= 10:
    bei = km * 500
else:
    bei = 10 * 500 + (km - 10) * 300

if mwanafunzi == "ndiyo":
    bei = bei * 0.5

print(f"Bei ya usafiri: {bei:,.0f} TZS")
# km 15, si mwanafunzi -> 5000 + 1500 = 6,500 TZS

Session 3 — Loops: while, for, range, break, continue + the Bahatisha Namba Game

Session flow

1. Homework review
2. while loop, counter, infinite loop and Ctrl+C
3. for loop over a string, range()
4. Break
5. break and continue, the while True pattern
6. Mini game: Bahatisha Namba (random) — we build it step by step
7. Review of the week
8. Q&A + homework

Explanation for the teacher (read this first)

• Loop = repeating a block of code many times.
• while sharti: — repeats as long as the condition is True. It checks the condition before each iteration. Something inside the loop must change the situation, otherwise the loop never ends (an infinite loop) → stop it with Ctrl + C (you will see KeyboardInterrupt).
• for kitu in mfuatano: (kitu = item, mfuatano = sequence) — goes through each element of a sequence (string, range, list...). Used when we know the number of iterations.
• range():
  • range(5) → 0, 1, 2, 3, 4 (does not include 5)
  • range(1, 6) → 1, 2, 3, 4, 5
  • range(0, 20, 5) → 0, 5, 10, 15
  • range(10, 0, -1) → 10, 9, ..., 1
• break — leave the loop immediately.
• continue — skip the rest of this iteration and go to the next one.
• Important pattern: while True: + break — for programs that repeat until the user says "acha" (stop).
• Accumulator pattern: jumla = 0 before the loop, jumla += x inside.
• random: import random at the top of the file; random.randint(1, 100) → a random number from 1 to 100 (both ends are included, unlike range).

Say this to the student

• "while is like eating rice: 'as long as you are still hungry, keep eating'. When you are full (the condition is False), you stop."
• "for is like a teacher calling names on a list — starts with the first, finishes with the last, each one once."
• "break is like a fire alarm — everyone leaves the building immediately. continue is like saying 'skip this one, go on to the next'."
• "An infinite loop is like a car with no brakes. Ctrl + C is the emergency brake."

Type this code live (share screen)

Step 1 — while (loops.py)

hesabu = 1
while hesabu <= 5:
    print("Mzunguko namba", hesabu)
    hesabu += 1
print("Loop imeisha")

Mzunguko namba 1
Mzunguko namba 2
Mzunguko namba 3
Mzunguko namba 4
Mzunguko namba 5
Loop imeisha

Then delete hesabu += 1 and run → infinite loop → Ctrl + C. "That's why something must change inside the loop."

Step 2 — Countdown

n = 5
while n > 0:
    print(n)
    n -= 1
print("Uzinduzi! 🚀")

Step 3 — for over a string

for herufi in "Python":
    print(herufi)

P
y
t
h
o
n

neno = "mamba"
idadi_a = 0
for h in neno:
    if h == "a":
        idadi_a += 1
print(f"Herufi 'a' ziko {idadi_a}")    # Herufi 'a' ziko 2

Step 4 — range()

for i in range(5):
    print(i, end=" ")       # 0 1 2 3 4
print()
for i in range(1, 6):
    print(i, end=" ")       # 1 2 3 4 5
print()
for i in range(0, 21, 5):
    print(i, end=" ")       # 0 5 10 15 20
print()
for i in range(10, 0, -2):
    print(i, end=" ")       # 10 8 6 4 2
print()

Step 5 — Multiplication table + total (accumulator)

n = int(input("Jedwali la namba gani? "))
for i in range(1, 11):
    print(f"{n} x {i:>2} = {n * i:>3}")

jumla = 0
for i in range(1, 101):
    jumla += i
print("Jumla ya 1 hadi 100 ni", jumla)   # 5050

Jedwali la namba gani? 7
7 x  1 =   7
7 x  2 =  14
...
7 x 10 =  70
Jumla ya 1 hadi 100 ni 5050

Step 6 — break and continue

for i in range(1, 11):
    if i == 7:
        break
    print(i, end=" ")
print()          # 1 2 3 4 5 6

for i in range(1, 11):
    if i % 3 == 0:
        continue
    print(i, end=" ")
print()          # 1 2 4 5 7 8 10

Step 7 — The while True pattern

jumla = 0
while True:
    maandishi = input("Weka namba (au 'q' kuacha): ")
    if maandishi == "q":
        break
    if not maandishi.isdigit():
        print("Hiyo si namba, jaribu tena.")
        continue
    jumla += int(maandishi)
print("Jumla:", jumla)

Step 8 — MINI GAME: Bahatisha Namba (bahatisha.py). Build it in 3 stages, running each stage.

Version 1 (one attempt):

import random

siri = random.randint(1, 20)
jaribio = int(input("Nimefikiria namba kati ya 1 na 20. Bahatisha: "))
if jaribio == siri:
    print("Umepata!")
else:
    print(f"Hapana, ilikuwa {siri}")

Version 2 (repeat until they get it, with hints):

import random

siri = random.randint(1, 20)
while True:
    jaribio = int(input("Bahatisha (1-20): "))
    if jaribio < siri:
        print("Juu zaidi ⬆")
    elif jaribio > siri:
        print("Chini zaidi ⬇")
    else:
        print("Umepata! 🎉")
        break

Version 3 (complete: limited attempts, counting, input checking, playing again):

import random

print("=== MCHEZO WA BAHATISHA NAMBA ===")

while True:                      # loop ya "cheza tena"
    siri = random.randint(1, 100)
    majaribio_max = 7
    majaribio = 0
    ameshinda = False

    print(f"\nNimefikiria namba kati ya 1 na 100. Una majaribio {majaribio_max}.")

    while majaribio < majaribio_max:
        jibu = input(f"Jaribio {majaribio + 1}: ").strip()
        if not jibu.isdigit():
            print("Tafadhali andika namba tu.")
            continue                 # haihesabiwi kama jaribio
        jaribio = int(jibu)
        if jaribio < 1 or jaribio > 100:
            print("Namba iwe kati ya 1 na 100.")
            continue
        majaribio += 1

        if jaribio < siri:
            print("Juu zaidi ⬆")
        elif jaribio > siri:
            print("Chini zaidi ⬇")
        else:
            print(f"Hongera! Umepata {siri} kwa majaribio {majaribio}.")
            ameshinda = True
            break

    if not ameshinda:
        print(f"Pole! Majaribio yamekwisha. Namba ilikuwa {siri}.")

    tena = input("Cheza tena? (ndiyo/hapana): ").strip().lower()
    if tena != "ndiyo":
        print("Kwaheri! 👋")
        break

Example:

=== MCHEZO WA BAHATISHA NAMBA ===

Nimefikiria namba kati ya 1 na 100. Una majaribio 7.
Jaribio 1: 50
Chini zaidi ⬇
Jaribio 2: 25
Juu zaidi ⬆
Jaribio 3: 37
Hongera! Umepata 37 kwa majaribio 3.
Cheza tena? (ndiyo/hapana): hapana
Kwaheri! 👋

Extra question to get them thinking: "What is the best guessing strategy?" → Start in the middle (50), then the middle of the remaining half (binary search). This way 7 attempts are always enough for 1–100 (2^7 = 128).

Note: emoji display well in the VS Code terminal. If a particular terminal shows strange symbols, remove them — they are not important.

Questions to ask the student

1. What numbers does range(3) give? — Answer: 0, 1, 2.
2. Can random.randint(1, 6) give 6? — Answer: Yes, it includes both ends.
3. When should we use while instead of for? — Answer: while when we don't know the number of iterations (e.g. until the user guesses correctly); for when we do (e.g. 10 times, or every character).
4. The difference between break and continue? — Answer: break leaves the whole loop; continue skips only this iteration.
5. What does this code print? for i in range(2, 10, 3): print(i) — Answer: 2, 5, 8.
6. How would you stop a stuck program? — Answer: Ctrl + C in the terminal.

Common mistakes

In-class exercise

1. Print all even numbers between 1 and 30 on one line.
2. Ask for a word; count the vowels (a, e, i, o, u) in it.

3. Draw a triangle of stars with a height chosen by the user:

   text

   Copy

   *
   **
   ***
   

4. Add to the guessing game: the user chooses a level (1 = easy 1–10, 2 = medium 1–50, 3 = hard 1–100).

# zoezi 1
for i in range(2, 31, 2):
    print(i, end=" ")
print()

# zoezi 2
neno = input("Neno: ").lower()
vokali = 0
for h in neno:
    if h in "aeiou":
        vokali += 1
print("Vokali:", vokali)

# zoezi 3
urefu = int(input("Urefu: "))
for i in range(1, urefu + 1):
    print("*" * i)

# zoezi 4 (sehemu ya kuongeza mwanzoni mwa mchezo)
import random

kiwango = input("Kiwango (1=rahisi, 2=kati, 3=kigumu): ").strip()
if kiwango == "1":
    juu = 10
elif kiwango == "2":
    juu = 50
else:
    juu = 100
siri = random.randint(1, juu)
print(f"Bahatisha namba kati ya 1 na {juu}")
while True:
    jaribio = int(input("Jaribio: "))
    if jaribio < siri:
        print("Juu zaidi")
    elif jaribio > siri:
        print("Chini zaidi")
    else:
        print("Umepata!")
        break

Homework

HW1 (after Session 1, bring to Session 2): barua_pepe.py (email) — ask for the first and last name; create an email in the format jina.mwisho@shule.ac.tz (lowercase, no spaces at the edges). Also display the username (the part before @) using .find("@") and slicing.

HW2 (after Session 2, bring to Session 3): kodi.py (tax) — ask for the monthly salary. Tax: up to 270,000 → 0%; 270,001–520,000 → 8%; 520,001–760,000 → 20%; over 760,000 → 25% (for simplicity, a percentage of the whole salary). Display the tax and the net salary using an f-string with commas.

HW3 (after Session 3, bring to the next session): fizzbuzz.py — for the numbers 1 to 30: if divisible by 3 write "Fizz", by 5 "Buzz", by 3 and 5 "FizzBuzz", otherwise the number itself. Bonus: pin.py — the user has 3 attempts to enter the correct PIN ("2580"); after 3 → "Kadi imezuiliwa" (card blocked).

# barua_pepe.py
kwanza = input("Jina la kwanza: ").strip().lower()
mwisho = input("Jina la mwisho: ").strip().lower()
email = f"{kwanza}.{mwisho}@shule.ac.tz"
print("Email:", email)
mahali = email.find("@")
print("Jina la mtumiaji:", email[:mahali])

# kodi.py
mshahara = float(input("Mshahara wa mwezi: "))
if mshahara <= 270000:
    kiwango = 0
elif mshahara <= 520000:
    kiwango = 0.08
elif mshahara <= 760000:
    kiwango = 0.20
else:
    kiwango = 0.25
kodi = mshahara * kiwango
print(f"Kodi: {kodi:,.0f} TZS")
print(f"Mshahara halisi: {mshahara - kodi:,.0f} TZS")

# fizzbuzz.py
for n in range(1, 31):
    if n % 15 == 0:          # lazima ikaguliwe kwanza!
        print("FizzBuzz")
    elif n % 3 == 0:
        print("Fizz")
    elif n % 5 == 0:
        print("Buzz")
    else:
        print(n)

# pin.py
PIN = "2580"
majaribio = 0
while majaribio < 3:
    pin = input("PIN: ")
    majaribio += 1
    if pin == PIN:
        print("Karibu!")
        break
    else:
        print(f"Si sahihi. Majaribio yaliyobaki: {3 - majaribio}")
else:
    print("Kadi imezuiliwa")

If you are asked a question you don't know

• Try it together in the REPL — strings and range are easy to test on the spot (list(range(2, 10, 3)) shows all the numbers in a range).
• Search: "python string methods", "python f-string format number", "python while vs for".
• Docs: https://docs.python.org/3/library/stdtypes.html#string-methods , https://docs.python.org/3/tutorial/controlflow.html , https://docs.python.org/3/library/random.html

End-of-week checklist

• Uses indexing (including negative) and knows the index starts at 0
• Does slicing [a:b], [:b], [a:], [::-1]
• Knows strings are immutable and writes s = s.upper()
• Uses methods: strip, lower/upper/title, replace, split, find, count, isdigit
• Writes f-strings with :.2f, :,
• Writes if/elif/else with : and correct indentation
• Understands why the order of elif matters
• Writes nested if
• Uses while and knows how to stop an infinite loop with Ctrl+C
• Uses for and range() (start, stop, step)
• Uses break, continue, and the while True pattern
• Has written a working Bahatisha Namba game