Useful List tricks in Python

list.py

#List traversal
range(start, stop, hop)
range(n) # [0,1,...,n-1]
range(1,n) # [1,...,n-1]
range(1,n,2) # [1,3,5,...,n-1] if n is even, or [1,3,5,...,n-2] if n is odd
range(n,-1,-1) # [n,n-1,n-2,...,0]
range(len(arr)) # Provides indices of an array arr
range(len(arr)-1,-1,-1) # Provides indices of arr backwards

# List slicing
arr[w:s] # Wait w elements, start copy (:), stop before reaching index s
arr = [1,2,3,4]
arr[1:] = [2,3,4]
arr[:2] = [1,2]

#List manipulation
arr = [1,2,3]
[str(x) for x in arr] # Output: ['1','2','3']
map(lambda x: str(x), arr) # Output: ['1','2','3']
[str(x) for x in arr if x%2] # Output: ['1','3']

# List as queue
arr = [1,2,3]
arr.append(x) # queue.push(x)
arr.pop(0) #queue.pop()
arr[0] #queue.peek()

# List as stack
arr = [1,2,3]
arr.append(x) #stack.push(x)
arr.pop() # stack.pop()
arr[-1] # stack.peek()