For Loops w/ Numeric Sequences

With studying Computer Science, we can use a lot of integers. By using range() function along with a for loop, we can start to analyze integer based sequences.

range() function

• The range() function can take 3 different arguments and it must have atleast 1 argument.

• The range() function is a function that generates an iterable sequence of integers in an arithmetic progression.

IMPORTANT NOTE: the result of a range() function is not printable by itself.

It must be converted to string or a list if you want to see the entire sequence.

Different Behaviours of: range()

NOTE: [ means inclusive, ( means exclusive mathematically.

Read more at this link.

1. range(n) returns a sequence of [0,n)

2. range(a,b) returns a sequence of [a,b); if a == b, it is an empty sequence

3. range(start, end, interval_value) returns a sequence of [start,end), but the sequence will approach the end value by adding each step with the interval value. if the interval_value is not specified, it is assumed to be 1.

NOTE: range() never includes the last/ending value.

Examples of range()

range(10) :: contains 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

range(10,21) :: contains 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20

range(2, 20, 4) :: contains 2, 6, 10, 14, 18

range(100, 0, -10) :: contains 100, 90, 80, 70, 60, 50, 40, 30, 20, 10

range(-10, -15, -1) :: contains -10, -11, -12, -13, -14

range(-5, 6) :: contains -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5

For Loops with range()

Since range() returns an iterable sequence, we can look through each individual values in it with a for loop.

Code

# Example 1
# For Loops with range()

for num in range(10):
    print('Current Number:', num)

# Examine that the iterating variable: num is going to represent each number
# in the sequence in order for each iteration of the for loop

Example

Current Number: 0
Current Number: 1
Current Number: 2
Current Number: 3
Current Number: 4
Current Number: 5
Current Number: 6
Current Number: 7
Current Number: 8
Current Number: 9

Code

# Example 2
# For Loops with range()

for negatives in range(-5,0):
    print('Negative values:', negatives)

Output

Negative values: -5
Negative values: -4
Negative values: -3
Negative values: -2
Negative values: -1

Code

# Example 3
# Finding the factors a number

target_value = 12

# Notice that we increase our end value of our range to include our target_value
for divider in range(1, target_value+1):
    if target_value % divider == 0:
        # found a factor
        print(divider, 'is a factor of', target_value)

Example

1 is a factor of 12
2 is a factor of 12
3 is a factor of 12
4 is a factor of 12
6 is a factor of 12
12 is a factor of 12