find val in list python code example

Example 1: python find in list

# There is several possible ways if "finding" things in lists.
'Checking if something is inside'
3 in [1, 2, 3] # => True
'Filtering a collection'
matches = [x for x in lst if fulfills_some_condition(x)]
matches = filter(fulfills_some_condition, lst)
matches = (x for x in lst if x > 6)
'Finding the first occurrence'
next(x for x in lst if ...)
next((x for x in lst if ...), [default value])
'Finding the location of an item'
[1,2,3].index(2) # => 1
[1,2,3,2].index(2) # => 1
[1,2,3].index(4) # => ValueError
[i for i,x in enumerate([1,2,3,2]) if x==2] # => [1, 3]

Example 2: python find index of first matching element in a list

# Basic syntax:
list.index(element, start, end) 
# Where:
#	- Element is the item you're looking for in the list
# 	- Start is optional, and is the list index you want to start at
#	- End is option, and is the list index you want to stop searching at

# Note, Python is 0-indexed

# Example usage:
my_list = [1, 2, 3, 4, 5, 6, 7, 8, 42, 9, 10]
my_list.index(42)
--> 8

Example 3: python index of item in list

list.index(element)