mylist = [[1, 'one'], [2, 'two'], [3, 'three'], 'four', 5]
i=0
while i<len(mylist):
	a=len(mylist[i])
	i+=1
	print(i,'element =', a)
	
input('enter')

a=mylist[i] # работает
a=len(mylist[i]) # не хочет

mylist = [[1, 'one'], [2, 'two'], [3, 'three'], 'four', 5]
i=0
while i<len(mylist):
	a=mylist[i]
	i+=1
	print(i,'element =', a)
	
input('enter')

1 element = [1, 'one']
2 element = [2, 'two']
3 element = [3, 'three']
4 element = 'four'
5 element = 5