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Python program to create a list centered on zero

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  • Last Updated : 17 Aug, 2022
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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]

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