Creating a list of integers

### 6.3.4 Creating a list of integers

The range command creates lists of equally spaced numbers. It can take one, two or three arguments.

- With one argument, range takes n, a positive integer.
- range(n) returns the list [0,1,…,n−1].
- Alternatively, range takes two mandatory and one optional argument:
  - a and b, two real numbers with a<b (unless the third argument p is provided and negative).
  - Optionally, p, a nonzero real number used for the step size (by default 1). If p<0, then a must be larger than b.
- range(a,b ⟨,p ⟩) returns the list [a,a+p,…] up to, but not including, b.

#### Examples

range(5)

| ⎡ ⎣ | 0,1,2,3,4 | ⎤ ⎦

range(4,10)

| ⎡ ⎣ | 4,5,6,7,8,9 | ⎤ ⎦

range(2.3,7.4)

| ⎡ ⎣ | 2.3,3.3,4.3,5.3,6.3,7.3 | ⎤ ⎦

range(4,13,2)

| ⎡ ⎣ | 4,6,8,10,12 | ⎤ ⎦

range(10,4,-1)

| ⎡ ⎣ | 10,9,8,7,6,5 | ⎤ ⎦

You can use the range command to create a list of values f(k), where k is an integer satisfying a certain condition. (See Section 25.3.3 for the for loop used below.)

You can list the values of an expression in a variable which goes over a range defined by range. For example:

[k^2+k for k in range(10)]

| ⎡ ⎣ | 0,2,6,12,20,30,42,56,72,90 | ⎤ ⎦

You can list the values of an expression in a variable which goes over a range defined by range and which satisfies a given condition. For example:

[k for k in range(4,10) if isprime(k)]

| ⎡ ⎣ | 5,7 | ⎤ ⎦

(See Section 7.1.14 for isprime.)

[k^2+k for k in range(1,10,2) if isprime(k)]

| ⎡ ⎣ | 12,30,56 | ⎤ ⎦