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Practicals

Python Theory

Arrays:

  • An array is a collection of elements. And it is used to store the multiple values in one variable.
  • The value of an array is called an element of the array.
  • An array can be of any type, for example int, char, float ..etc.

    • Or

    Arrays elements are mutable which means they are changeable i.e we can add elements and remove elements easily.

    Is a python list the same as an array?

  • Python arrays and lists have the same way of storing data.
  • Arrays take only a single data type element but lists can have any type of data.
  • Therefore, other than a few operations the kind of operations performed on them are different.
    • How to create arrays in python?
  • An arrays in python can be created importing the array module.
  • An array in python can be defined as the following ways.

    • import array as arr

    The array(data type,value list) takes two parameters.

  • The first one is data type of the value to be stored.
  • The second is the value list.
    • Syntax
    a =arr.array(data type,value List)
    or a =array(data type,value List)
    Example
    import array
    a =array.array('i',[1,2,3,45,67,9])
    print(a)

    import array as arr
    array =arr.array('i',[1,2,3,4,5,6])

    print(a)

    from array import *
    a =array('i',[1,2,3,4,5,6])
    print(a)
    CodeC codePython Data TypeByte
    i Signed intint2
    I Unsigned intInt2
    u unicodeunicode2
    HUnsigned short Unsigned short2
    hSigned shortSigned short2
    lSigned longSigned long4
    LUnsigned longUnsigned long4
    fFloatFloat4
    dDoubleFloat4

    Accessing array elements:

  • Access elements using index values.
  • Indexing starts at 0 and not from 1 .Hence,the index is always 1 less than the length of the array.
  • Negative index values can be used as well.The point to remember is that negative indexing starts from the reverse order from right to left.
    • Syntax
    Array_name[index value]
    Example
    import array as arr
    a =arr.array('i',[4,3,5,7])

    print("First element:", a[0])
    print("Last element:", a[-1])
    Output
    SkillPundit: Python-Accessing-Array

    Slicing Python Arrays:

    An array can be sliced using the : symbol. This returns a range of elements that we have specified by the index numbers.

    Example
    import array as arr
    a =arr.array('i',[4,3,5,7])

    print(a[1:3])
    print(a[:-2])
    print(a[:])
    Output
    SkillPundit: Python-Slicing-Array

    Finding the length of the array

  • Length of an array is the number of elements that are actually present in an array
  • You can make use of the len() function to achieve this.
    • Syntax
    len(arry_name)
    Example
    import array as arr
    a =arr.array('i',[1.1,2.1,3.1])

    len(a)

    Changing and Adding Elements:

  • Arrays are mutable.
  • Elements can be changed in a similar way of lists.
    • Example
    import array as arr
    a =arr.array('i',[1,2,3,4,5])

    #changing first element
    a [0]=0
    print(a)

    #changing 2nd and 4th element
    a [1:5]=arr.array('i',[4,6,8])
    print(a)
    Output
    SkillPundit: Python-Changing and Adding Elements

    Adding elements to an array:

    MethodDescription
    append() Used when you want to add a single element at the end of an array.
    extend() Used when you want to add more than one element at the end of an array.
    Insert() Used when you want to add an element at a specific position in an array
    Example
    import array as arr
    a =arr.array('i',[1,2,3])
    a.append(4)
    print(a)

    b =arr.array('d',[1.1,2.3])
    b.extend([1.5,3])
    print(b)

    c =arr.array('i',[9,3,4])
    c.insert(2,34)
    print(c)
    Output
    SkillPundit: Python-Adding-Elements to an array

    Removing elements of an array:

    MethodDescription
    pop() Used when you want to remove an element and return it.
    remove() Used when you want to remove an element with a specific value without returning it .
    Example
    import array as arr
    a =arr.array('d',[1,2,3,4,5])
    a.pop( )
    print(a)
    a.pop(3)
    print(a)
    a.remove(2)
    print(a)
    Output
    SkillPundit: Python-Removing-Elements of an array

    Array concatenation:

    Concatenation two arrays Using “+” symbol

    Example
    # Concatenation of two arrays
    import array as arr

    a =arr.array('i',[1,3,5])
    b =arr.array('i',[2,4,6])
    c=a+b

    print(c)
    Output
    SkillPundit: Python-SkillPundit: Python-Array_Concatenation

    Looping through array:

    We can loop through an array easily using the for and while loops

    MethodDescription
    for() Iterates over the items of an array specified number of times.
    while() Iterates over the elements until a certain condition is met.
    Example
    import array as arr
    a =arr.array('d',[1,2,3,4,5])
    print("All Values:")
    for x in a:
    print(x)
    Output
    SkillPundit: Python-SkillPundit: Python-Looping_Array