Using the count() Method in Python Lists: Code Examples and Applications

📚 Quick Study Guide

• 🔍 The count() method in Python lists returns the number of times a specified value appears in the list.
• 🔢 The syntax is: list_name.count(value) where list_name is the name of your list and value is what you're counting.
• 💡 If the value doesn't exist in the list, count() returns 0.
• 📜 The method is case-sensitive for strings. "Apple" and "apple" are considered different.
• ⏱️ count() has a time complexity of O(n), where n is the length of the list.
• 🐍 It works with any data type stored in the list (integers, strings, booleans, etc.).
• 💾 The original list remains unchanged; count() just returns a value.

Practice Quiz

1. What does the count() method do in Python lists?

   1. Counts the number of elements in a list.
   2. Returns the index of the first occurrence of a specified value.
   3. Returns the number of times a specified value appears in the list.
   4. Sorts the list.

2. What is the return value of [1, 2, 2, 3].count(2)?

   1. 1
   2. 2
   3. 3
   4. 0

3. What will ['a', 'b', 'a', 'c'].count('A') return?

   1. 2
   2. 1
   3. Error
   4. 0

4. If a list is empty, what will [].count(5) return?

   1. Error
   2. 1
   3. -1
   4. 0

5. What is the time complexity of the count() method?

   1. O(1)
   2. O(log n)
   3. O(n)
   4. O(n^2)

6. Does the count() method modify the original list?

   1. Yes, it sorts the list first.
   2. Yes, it removes the counted element.
   3. No, it returns a new list.
   4. No, the original list remains unchanged.

7. What will be the output of the following code?

   my_list = [True, False, True, True]
   print(my_list.count(True))

   1. 1
   2. 2
   3. 3
   4. False