# Python: for Loop

## Loop through range

### Case #1

``````# Loop through a range of numbers
# starting from 0 to 4
# as range(n) return number from 0 to n-1
for i in range(5):
print(i)``````
Python

Output:

``````0
1
2
3
4``````
Plaintext

### Case #2

``````# Loop through a range of numbers
# starting from 5 to maximum 19(=20-1), and each step is 3 numbers
for i in range(5, 20, 3):
print(i)``````
Python

Output:

``````5
8
11
14
17``````
Plaintext

## Loop through Tuple

``````items = (5, 10, 15, 20, 25, 30)

for i in items:
print(i)``````
Python

Output:

``````5
10
15
20
25
30``````
Plaintext

## Loop through Set

``````items = {5, 10, 15, 20, 25, 30}

for i in items:
print(i)``````
Python

Output:

``````20
5
25
10
30
15``````
Plaintext

## Loop through List items

### Case #1

``````for i in [5, 10, 15, 20, 25, 30]:
print(i)``````
Python

Output:

``````5
10
15
20
25
30``````
Plaintext

### Case #2

We can enumerate a list and loop through it to get the key and value-

``````items = [5, 10, 15, 20, 25, 30]

for key, value in enumerate(items):
print(f"Key: {key} || Value: {value}")``````
Python

Output:

``````Key: 0 || Value: 5
Key: 1 || Value: 10
Key: 2 || Value: 15
Key: 3 || Value: 20
Key: 4 || Value: 25
Key: 5 || Value: 30``````
Plaintext

### Case #3

Let’s see how we can find the largest number of a list using a for loop-

``````# Array of positive integers
items = [523, 687, 271, 99, 401, 178, 366, 836, 290, 730, 444, 123, 76, 357, 456, 679]

# Initialize with 0
largestNum = 0

# Loop through the array
# and try to find the largest number
for item in items:
if item > largestNum:
largestNum = item

# For debugging purpose
print("largestNum is updated to: ", largestNum)

print("\n\nLargest number: ", largestNum)``````
Python

Output:

``````largestNum is updated to:  523
largestNum is updated to:  687
largestNum is updated to:  836

Largest number:  836``````
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### Case #4

We can also calculate the sum of the numbers looping through the numbers by looping though each item and adding that to the sum-

``````# Array of integers
items = [523, 687, 271, 99, 401, 178, 366, 836, 290, 730, 444, 123, 76, 357, 456, 679]

# Initialize with 0
total = 0

# Loop through the array
# and calcualte the sum
for item in items:
total += item

print("Total value: ", total)``````
Python

Output:

``Total value:  6516``
Plaintext

## Loop through Dictionary items

### Case #1

``````# Dictionary of capitals of different countries
country_capitals = {
"United Kingdom": "London",
"France": "Paris",
"Germany": "Berlin",
"Japan": "Tokyo",
"China": "Beijing",
"India": "New Delhi",
"Russia": "Moscow",
"Australia": "Canberra",
"United States": "Washington, D.C.",
}

# Loop through the dictionary items
for country, capital in country_capitals.items():
print(f"Country: {country} || Capital: {capital}.")
``````
Python

Output:

``````Country: United Kingdom || Capital: London.
Country: France || Capital: Paris.
Country: Germany || Capital: Berlin.
Country: Japan || Capital: Tokyo.
Country: China || Capital: Beijing.
Country: India || Capital: New Delhi.
Country: Russia || Capital: Moscow.
Country: Australia || Capital: Canberra.
Country: United States || Capital: Washington, D.C..``````
Plaintext