Find the First Instance of a Nonzero Number in a List in Python

Find the first instance of a nonzero number in a list in Python

Use next with enumerate:

>>> myList = [0.0 , 0.0, 0.0, 2.0, 2.0]
>>> next((i for i, x in enumerate(myList) if x), None) # x!= 0 for strict match
3

Find first instance of non zero number in list after an index value

You can try this one !

myarray=[45,45,1,0,0,0,8,6,7]

def firstNon0(_list,startindex):
    for index in range(startindex,len(_list)):
        if _list[index]!=0:return index
    return None

print myarray[firstNon0(myarray,3)]


>>8

how to find first index of any number except 0 in python list?

You could use enumerate to iterate over the indices and values. Then use next to stop upon finding the first non-zero value. If StopIteration was thrown, the list contained no non-zero values, so do whatever error handling you'd like there.

def first_non_zero(values):
    try:
        return next(idx for idx, value in enumerate(values) if value != 0)
    except StopIteration:
        return None

Examples

>>> list1 = [0,0,0,0,4,3,2,0,3]
>>> first_non_zero(list1)
4
>>> first_non_zero([0,0,0])
>>>      # None

Find first instance of non zero number in list after an index value

You can try this one !

myarray=[45,45,1,0,0,0,8,6,7]

def firstNon0(_list,startindex):
    for index in range(startindex,len(_list)):
        if _list[index]!=0:return index
    return None

print myarray[firstNon0(myarray,3)]


>>8

Find first non zero numbers in an array (zeroes can be anywhere)

You can do this

x = [10,0,30,40]
for var in x:
    if var != 0:
        y = var
        break

how do I capture the first non-zero integer from the back of an integer?

To achieve this you should first convert the integer 'n' to a string and iterate through it in the reverse order.
Below is the code for demonstrating this.

  def last_digit(n): 
    n=str(n)
    rev=n[::-1] # Reversing the string 'n'
    for i in rev:
        if i!='0' :
            print(i)
            break 

The first non-zero element in each row

If I understood correctly, the break should be inside the if statement

if a[i,j]!=0:
      print(i+1,'-th row,',j+1,'-th column','\nthe 1st non-zero element:',a[i,j],'\n---')
      break

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