In this article, we will discuss how to create a Python List of numbers from 1 to N.
Table Of Contents
Introduction
Suppose value of N is 15, then the list should contain numbers from 1 to 15. Like this,
[1, 2, 3, 4, 5, 6 ,7, 8, 19, 10, 11, 12, 13, 14, 15]
There are different ways to create a list containing numbers from 1 to N. Let’s dicuss them one by one,
Method 1: Using range() function
The range() function in Python, accepts three arguments i.e. start, stop and step. It returns a sequence of integers from start (inclusive) to stop (exclusive) by given step.
To create a list of numbers from 1 to N, we will pass start as 1, and stop as N + 1. Default value of step size is 1. Therefore, it will return a sequence of numbers from 1 to N. Then we can cast that sequence to a list.
Let’s see some examples,
Example 1: With step size 1
In this example, we will create a sequence of numbers from 1 to 15.
N = 15 # Get a list of numbers from 1 to N (including N) numbers = list(range(1, N + 1)) print(numbers) # Print the type of numbers object print(type(numbers))
Output:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
We created a List of numbers from 1 to N, where N is 15.
Example 2: With step size 2
In this example, we will create a sequence of numbers from 1 to 15, with step size 2. It will keep every alternate number from 1 to 15.
N = 15 # Get a list of every alternate numbers from 1 to N (including N) numbers = list(range(1, N + 1, 2)) print(numbers)
Output:
[1, 3, 5, 7, 9, 11, 13, 15]
We creates a list of numbers from 1 to 15, but with step size 2. It means, list contains every alternate number from 1 to 15.
Method 2: Using numpy.arange() function
The arange() function of NumPy module, accepts three arguments i.e. start, stop and step. It returns a numpy array of integers from start (inclusive) to stop (exclusive) by the given step size.
To create a list of numbers from 1 to N, we will pass start as 1, and stop as N + 1. Default value of step size is 1. Therefore, it will return an array of numbers from 1 to N. Then we can call the tolist() function of array, to convert it to a list of numbers.
Example 1: With step size 1
In this example, we will create a sequence of numbers from 1 to 15.
import numpy as np N = 15 # Get a list of numbers from 1 to N (including N) numbers = np.arange(1, N+1).tolist() print(numbers)
Output:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
We created a List of numbers from 1 to N, where N is 15.
Example 2: With step size 2
In this example, we will create a sequence of numbers from 1 to 15, with step size 2. It will keep every alternate number from 1 to 15.
import numpy as np N = 15 # Get a list of every alternate numbers from 1 to N (including N) numbers = np.arange(1, N+1, 2).tolist() print(numbers)
Output:
[1, 3, 5, 7, 9, 11, 13, 15]
We creates a list of numbers from 1 to 15, but with step size 2. It means, list contains every alternate number from 1 to 15.
Method 3: Using while loop
Create an empty list. Then use the while loop to iterate from 1 till N, and for each ith number in loop, append number i to the list. This way our list will have numbers from 1 till N.
Let’s see an example, in which we will create a sequence of numbers from 1 to 15.
# Create an empty list
numbers = []
N = 15
i = 1
# Iterate from 1 till N
while i <= N:
numbers.append(i)
i = i + 1
print(numbers)
Output:
[1, 3, 5, 7, 9, 11, 13, 15]
We creates a list of numbers from 1 to 15.
Method 4: Using List Comprehension
To create a list of numbers from 1 to N. Pass the 1, and N+1 to the range() function. It will give a sequence of numbers from 1 to N. Then create a list from them, using List Comprehension. Let’s see an example,
N = 15 # Create a list of numbers from 1 to N numbers = [i for i in range(1, N+1)] print(numbers)
Output:
[1, 3, 5, 7, 9, 11, 13, 15]
We creates a list of numbers from 1 to 15.
Summary
We learned about four different ways to create a list of numbers from 1 till N. Thanks.