python-doc/Docs/Basic/04-operators.md

1. for Loop with range()

for i in range(2, 20, 1):
    print(f"i : {i}", end=" End \n")

• range(start, stop, step): Generates a sequence of numbers starting from start (inclusive), up to stop (exclusive), increasing by step.
  • range(2, 20, 1) → numbers from 2 to 19 (inclusive), step 1.
• for loop: Iterates over each number in the range.
• print(f"i : {i}", end=" End \n"):
  • f-string: Formats the output with the current value of i.
  • end=" End \n": Replaces the default newline (\n) with " End " followed by a newline.
• Output: Prints each number with " End " at the end of each line.

---

2. Looping Through a List Using Index and enumerate()

list = ['abbas', 'mmd', 2006]
for key in range(len(list)):
    value = list[key]
    print(key, value)

• len(list): Returns the number of elements in the list (3).
• range(len(list)): Creates numbers 0, 1, 2 (indices of the list).
• list[key]: Accesses the element at index key.
• Output: Prints index and value pair for each element.

---

for key, value in enumerate(list):
    print(key, value)

• enumerate(list): Returns pairs of (index, value) for each element.
• key, value: Unpacks each pair into two variables.
• Output: Same as above, but more concise and Pythonic.

✅ Best Practice: Use enumerate() instead of range(len()) for cleaner code.

---

3. zip() Function – Pairing Two Lists

name = ['egg', 'oil']
price = [370000, 500000]
for final in zip(name, price):
    print(final)

• zip(list1, list2): Combines two lists element-wise into tuples.
  • zip(['egg', 'oil'], [370000, 500000]) → [('egg', 370000), ('oil', 500000)]
• for final in zip(...): Iterates over each tuple.
• Output: Prints each pair as a tuple.

✅ Use zip() when you need to process multiple lists in parallel.

---

Summary of Key Concepts:

Concept	Purpose
range(start, stop, step)	Generate a sequence of numbers
for loop	Iterate over a sequence
len(list)	Get number of elements
enumerate()	Get index and value in a loop
zip()	Combine two or more lists element-wise