Python | First occurrence of True number
Many times we require to find the first occurring non-zero number to begin the processing with. This has mostly use case in Machine Learning domain in which we require to process data excluding None or 0 values. Let’s discuss certain ways in which this can be performed.
Method #1 : Using next() + enumerate()
The next function can be used to iterate through the list and enumerate along with it checks for the list if the number is a non zero element and returns the number of 0s before a True value i.e a non zero value.
# Python3 code to demonstrate # finding first True value # using next() and enumerate() # initializing list test_list = [ 0, 0, 5, 6, 0] # printing original list print ("The original list is : " + str(test_list)) # finding first True value # using next() and enumerate() res = next((i for i, j in enumerate(test_list) if j), None) # printing result print ("The values till first True value : " + str(res)) |
chevron_right
filter_none
Output:
The original list is : [0, 0, 5, 6, 0] The values till first True value : 2
Method #2 : Using filter() + lamda + index()
Using the combination of the above functions, one can easily perform this particular task. The filter function can be used to screen out the True value that is processed by the lambda functions and index function returns the first occurrence of this.
# Python3 code to demonstrate # finding first True value # using filter() + lamda + index() # initializing list test_list = [ 0, 0, 5, 6, 0] # printing original list print ("The original list is : " + str(test_list)) # finding first True value # using filter() + lamda + index() res = test_list.index(next(filter(lambda i: i != 0, test_list))) # printing result print ("The values till first True value : " + str(res)) |
chevron_right
filter_none
Output:
The original list is : [0, 0, 5, 6, 0] The values till first True value : 2
Recommended Posts:
- Python | Add the occurrence of each number as sublists
- Python | True Record
- Python | Matrix True Summation
- Python | Segregate True and False value indices
- Python | Count true booleans in a list
- Python - Test if a list is completely True
- Python | Get indices of True values in a binary list
- Python | Test if any list element returns true for condition
- Python program to fetch the indices of true values in a Boolean list
- Python - Slice from Last Occurrence of K
- Python | Find last occurrence of substring
- Python - Sum of each List element occurrence in another
- Python - Substitute K for first occurrence of elements
- Python | Split on last occurrence of delimiter
- Python | Get the string after occurrence of given substring
- Python | K occurrence element Test
- Python | Last occurrence of some element in a list
- Python | Substitute character with its occurrence
- Python - Consecutive Alphabetic Occurrence
- Python - Remove first occurrence of K in Tuple
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.
