Python program to create a list centered on zero

Given two integer variables, limit and diff, write a Python program to create a list that is centered on zero, using limit, which specifies limit of the list and diff that specifies the common difference between integers. 

Examples:

Input : limit = 1, diff = 0.5
Output : [-1, -0.5, 0.0, 0.5, 1]

Input : limit = 25, diff = 5
Output : [-25, -20, -15, -10, -5, 0, 5, 10, 15, 20, 25]

Approach #1: Naive Approach 

This is a naive approach to the above problem. First, create an empty list ‘lst’, and then we use a while loop to append the next integer with a difference equal to ‘diff’. 

Python3

# Python3 program to Convert a
# list to dictionary

def create(limit, diff):

    lst = [-limit]
    while lst[-1] < limit:
        lst.append(lst[-1] + diff)
    lst[-1] = limit
    return lst

# Driver code
limit = 1
diff = 0.5
print(create(limit, diff))

Output:

[-1, -0.5, 0.0, 0.5, 1]

Approach #2: Using Python Numpy 

Using Numpy module makes the solution a lot easier. In this method, we use np.arange which return evenly spaced values within a given interval ‘diff’. 

Python3

# Python3 program to Convert a
# list to dictionary
import numpy as np

def create(limit, diff):
    lst = np.arange(diff, limit, diff)
    if (lst[-1] != limit):
        lst = np.r_[lst, limit]

    return np.r_[-lst[::-1], 0, lst].tolist()

# Driver code
limit = 1
diff = 0.5
print(create(limit, diff))

Output:

[-1.0, -0.5, 0.0, 0.5, 1.0]

Approach #3: list comprehension

Python3

# Python3 program to create a list centered on zero

def create(limit, diff):
    length = int(((limit/diff)*2)+1)
    list = [-limit+i*diff for i in range(length)]
    return list


# Driver code
limit = 1
diff = 0.5
print(create(limit, diff))

Output:

[-1.0, -0.5, 0.0, 0.5, 1.0]