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      Reverse Arrays

      Python Tutorial

      This Python tutorial has been written for the beginners to help them understand the basic to advanced concepts of Python Programming Language. After completing this tutorial, you will find yourself at a great level of expertise in Python, from where you can take yourself to the next levels to become a world class Software Engineer.

      Reverse Arrays

      In this chapter, we shall explore the different ways to rearrange the given array in the reverse order of the index. In Python, array is not one of the built-in data types. However, Python's standard library has array module. The array class helps us to create a homogenous collection of string, integer or float types.
      
      The syntax used for creating array is 
      import array
      obj = array.array(typecode[, initializer])
      Let us first create an array consisting of a few objects of int type
      import array as arr
      a = arr.array('i', [10,5,15,4,6,20,9])
      The array class doesn't have any built-in method to reverse array. Hence, we have to use another array. An empty array "b" is declared as follows
      b = arr.array('i')
      Next, we traverse the numbers in array "a" in reverse order, and append each element to the "b" array −
      for i in range(len(a)-1, -1, -1):
      b.append(a[i])
      Te array "b" now holds numbers from original array in reverse order.

      Example 1

      Here is the complete code to reverse an array in Python
      import array as arr
      a = arr.array('i', [10,5,15,4,6,20,9])
      b = arr.array('i')
      for i in range(len(a)-1, -1, -1):
         b.append(a[i])
      print (a, b)
      It will produce the following output 
      array('i', [10, 5, 15, 4, 6, 20, 9]) array('i', [9, 20, 6, 4, 15, 5, 10])
      We can also reverse the sequence of numbers in an array using the reverse() method in list class. List is a built-in type in Python.
      We have to first transfer the contents of an array to a list with tolist() method of array class
      a = arr.array('i', [10,5,15,4,6,20,9])
      b = a.tolist()
      We can call the reverse() method now
      b.reverse()
      If we now convert the list back to an array, we get the array with reversed order,
      a = arr.array('i')
      a.fromlist(b)

      Example 2

      Here is the complete code
      from array import array as arr
      a = arr.array('i', [10,5,15,4,6,20,9])
      b = a.tolist()
      b.reverse()
      a = arr.array('i')
      a.fromlist(b)
      print (a)
      It will produce the following output
      array('i', [10, 5, 15, 4, 6, 20, 9])

      Practice with Online Editor

      Note: This Python online Editor is a Python interpreter written in Rust, RustPython may not fully support all Python standard libraries and third-party libraries yet.
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