Arrays in Python
Reverse an array arr = [1, 2, 3, 4, 5, 6, 7, 8] reversedArray = arr[::-1] # [8, 7, 6, 5, 4, 3, 2, 1] arr[3:5] = arr[3:5][::-1] Slices with step s[i:j:k] means “slice of s from i to j with step k”. When i and j are absent, the whole sequence is assumed and thus s[::k] means “every k-th item” in the entire sequence. s = range(20) # output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] # 3rd item from s: s[::3] # output: [0, 3, 6, 9, 12, 15, 18] # 3rd item from s[2:]: s[2:] # output: [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] s[2::3] # output: [2, 5, 8, 11, 14, 17] # 3rd item from s[5:12]: s[5:12] # output: [5, 6, 7, 8, 9, 10, 11] s[5:12:3] # output: [5, 8, 11] # 3rd item from s[:10]: s[:10] # output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] s[:10:3] # output: [0, 3, 6, 9] Clone a list newArr = oldArr[:]