Минималистичный код

text = "Ура! Каникулы!!! Не учимся!"

# 1

chr_count = sum(1 for i in text if i == "!")

text = text.replace("!", "")

print("Номер 1")

print(text)

print(chr_count)

# 2

text = text.replace("а", "абвгд")

print("nНомер 2")

print(text)

# 3

text = text + text[::-1]

print("nНомер 3")

print(text)

# 4

text = text[::2]

print("nНомер 4")

print(text)

Код с циклами

text = "Ура! Каникулы!!! Не учимся!"

# 1

chr_count = 0

chr_num = 0

for _ in text:

if text[chr_num] == "!":

chr_count += 1

text = text[:chr_num] + text[chr_num+1:]

continue

chr_num += 1

print("Номер 1")

print(text)

print(chr_count)

# 2

chr_num = 0

for i in text:

if text[chr_num] == "а":

text = text[:chr_num+1] + "бвгд" + text[chr_num+1:]

chr_num += 4

chr_num += 1

print("nНомер 2")

print(text)

# 3

new_text = text

for num in range(1, len(text)+1):

new_text += text[-num]

text = new_text

print("nНомер 3")

print(text)

# 4

new_text = ""

for num in range(len(text)):

if num % 2 == 0:

new_text += text[num]

text = new_text

print("nНомер 4")

print(text)