Table of Contents(目次)
Mastering the range() Function
In this lecture, we’ll take a closer look at the range() function, which is often used together with the for loop.
Basics of the range() Function
Basically, range() returns a sequence of numbers starting from 0 when you pass a single integer as an argument. When you provide multiple arguments, you can control the range of numbers generated—similar to how list slicing works.
Arguments and Returned Integers
range(n): Returns integers from0up ton - 1.- If
nis a negative value or 0, no numbers are returned, and theforloop terminates without running even once. - If
nis greater than or equal to 1, the loop will iterate n times.range(3):0 → 1 → 2
- If
range(n, m): Returns integers fromnup tom - 1.- Pass arguments such that
n < m.range(1, 5):1 → 2 → 3 → 4
- If
n > m, nothing is returned.range(5, 1): # returns nothing
- If
n < m, you can also use negative values.range(-5, 0):-5 → -4 → -3 → -2 → -1
- Pass arguments such that
range(n, m, step): When you specify thestepvalue, it extracts elements fromrange(n, m)at intervals ofstep.- Unlike list slicing, both
nandmmust be explicitly defined.-
range(1, 20, 5):1 → 6 → 11 → 16
-
- You can also specify a negative value for
step.- When a negative value is used, numbers are generated in reverse order. In this case,
nandmmust satisfy the conditionn > m. range(5, 1, -1):5 → 4 → 3 → 2
- When a negative value is used, numbers are generated in reverse order. In this case,
- Unlike list slicing, both
1. Basics of range(n)
range(n) generates integers sequentially from 0 to n - 1.
for i in range(5):
print(i)
Example Output:
0
1
2
3
4
2. Using range(n, m)
range(n, m) generates integers from n to m - 1. Unlike list slicing, n cannot be omitted.
for i in range(2, 6):
print(i)
Example Output:
2
3
4
5
3. Specifying Steps with range(n, m, step)
range(n, m, step) generates integers from n to m - 1 in increments of step. The step value can be either positive or negative.
for i in range(1, 10, 2):
print(i)
Example Output:
1
3
5
7
9
When a negative step is specified, numbers are generated in reverse order.
for i in range(5, 0, -1):
print(i)
Example Output:
5
4
3
2
1
