# Python | Valid Ranges Product

Many times we need to get the product 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 product 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 product once we find a next value to be zero and append it in result list.

 `# Python3 code to demonstrate ` `# Valid Ranges Product ` `# 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 ` `# Valid Ranges Product ` `res ``=` `[] ` `val ``=` `1` `for` `ele ``in` `test_list: ` `    ``if` `ele ``=``=` `0``: ` `        ``if` `val !``=` `1``: ` `            ``res.append(val) ` `            ``val ``=` `1` `    ``else``: ` `        ``val ``*``=` `ele ` ` `  `# print result ` `print``(``"The non-zero group product of list is : "` `+` `str``(res)) `

Output :

```The original list : [4, 9, 0, 0, 3, 4, 5, 0, 0, 4, 0]
The non-zero group product of list is : [36, 60, 4]
```

Method #2 : Using `itertools.groupby()` + loop
This particular task can also be performed using groupby function to group all the non-zero values and product can be performed using loop.

 `# Python3 code to demonstrate ` `# Valid Ranges Product ` `# Using itertools.groupby() + loop ` `from` `itertools ``import` `groupby ` ` `  `# getting Product ` `def` `prod(val) : ` `    ``res ``=` `1`  `    ``for` `ele ``in` `val: ` `        ``res ``*``=` `ele ` `    ``return` `res  ` `     `  `# 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() + loop ` `# Valid Ranges Product ` `res ``=` `[prod(val) ``for` `keys, val ``in` `groupby(test_list, key ``=` `lambda` `x: x !``=` `0``) ``if` `keys !``=` `0``] ` ` `  `# print result ` `print``(``"The non-zero group product of list is : "` `+` `str``(res)) `

Output :

```The original list : [4, 9, 0, 0, 3, 4, 5, 0, 0, 4, 0]
The non-zero group product of list is : [36, 60, 4]
```

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