Python – Find minimum of non zero groups

Many times we need to get the minimum of not the whole list but just a part of it and at regular intervals. These intervals are sometimes decided statically before traversal, but sometimes, the constraint is more dynamic and hence we require to handle it in more complex way. Criteria discussed here is minimum of non-zero groups. Let’s discuss certain ways in which this task can be done.

Method #1 : Using loops
This task can be performed using the brute force manner using the loops. We just traverse the list each element to test for it’s succeeding element to be non-zero value and perform the minimum once we find a next value to be zero and append it in result list.

# Python3 code to demonstrate
# Natural Numbers Minimum
# Using loops

# initializing list
test_list = [4, 9, 0, 0, 3, 4, 5, 0, 0, 4, 0]

# printing original list
print("The original list : " + str(test_list))

# using loops
# Natural Numbers Minimum
res = []
val = 99999
for ele in test_list:
    if ele == 0:
        if val != 99999:
            res.append(val)
            val = 99999
    else:
        val = min(val, ele)

# print result
print("The non-zero group Minimum of list is : " + str(res))

Output :

The original list : [4, 9, 0, 0, 3, 4, 5, 0, 0, 4, 0]
The non-zero group Minimum of list is : [4, 3, 4]

Method #2 : Using itertools.groupby() + min()
This particular task can also be performed using groupby function to group all the non-zero values and min function can be used to perform their minimum.

# Python3 code to demonstrate
# Natural Numbers Minimum
# Using itertools.groupby() + min()
from itertools import groupby

# initializing list
test_list = [4, 9, 0, 0, 3, 4, 5, 0, 0, 4, 0]

# printing original list
print("The original list : " + str(test_list))

# using itertools.groupby() + min()
# Natural Numbers Minimum
res = [min(val) for keys, val in groupby(test_list, key = lambda x: x != 0) if keys != 0]

# print result
print("The non-zero group minimum of list is : " + str(res))

Output :

The original list : [4, 9, 0, 0, 3, 4, 5, 0, 0, 4, 0]
The non-zero group Minimum of list is : [4, 3, 4]