Page 148 - Computer Science V2.0 Class 11

6.3.3 Multiple Assignments
Assigning a value to several variables: Sometimes, we need to assign the same value (say, 0 or 100) to several variables.
Python allows us to use multiple variables in a single assignment statement by using a comma(,) as a delimiter. Let
us learn the different ways to make multiple assignments. For example, suppose we are given a square matrix, and
we want to find the sum of all elements of the matrix, the sum of the main diagonal elements (trace) of the matrix,
the sum of the corner elements of the matrix, and the sum of the antidiagonal elements of the matrix. To do these
computations, we would like to initialise these quantities as 0. The following assignment statement will assign the
value 0 to variables sumMatrix, trace, sumCorners, and sumAntidiag.
sumMatrix = trace = sumCorners = sumAntidiag = 0
In general, Python uses the following syntax for assigning the same value to multiple variables
<identifier_1> = <identifier_2> = ... = <identifier_N> = <value>
The above description extends the notation for Python syntax, described earlier. While the text in the angular brackets
is replaced by the appropriate Python expressions, the keywords and the operators appear as they are. The ellipses
indicate multiple occurrences of a syntactic construct. Let us examine the following Python statement in light of the
above description of the multiple assignments.:
sumMatrix = trace = sumCorners = sumAntidiag = 0
In the above statement, <identifier_1> is replaced by sumMatrix, the equal to symbol (=) appears in the
Python statement as it appears in the syntax description, Next, the syntax<identifier_2> ... = <identifier_
N> implies that a variable name may be followed by the equal to symbol any number of times. So, it is fine to follow
sumMatrix = by trace = sumCorners = sumAntidiag =. Finally, <value> in the syntax description is
replaced by 0 (a valid value) to form the assignment statement:

sumMatrix = trace = sumCorners = sumAntidiag = 0
Assigning multiple values to multiple variables: Sometimes we need to assign multiple values to multiple variables.
The following syntax enables us to assign multiple values (possibly different, but not necessarily) to multiple variables.

<identifier_1>, <identifier_2>, ..., <identifier_N> = <value1>, <value2>, ..., , <valueN>
The above statement will assign different values <value1>, <value2>, ..., , <valueN> to the variables
<identifier_1>, <identifier_2>, ..., <identifier_N>, respectively. Consider the following example:

>>> day, month, year = 15, 8, 2022
>>> print('Independence Day:', day, month, year)
Independence Day: 15 8 2022
In the above example, the variable day is assigned the value 15, the variable month is assigned the value 8, and the
variable YEAR is assigned the value 2022. An expression appearing on the right-hand side (RHS) of the assignment
operator is evaluated first, and thereafter, the result is assigned to the respective variable on the left-hand side (LHS).
The expressions are evaluated in the order of left to right. This is explained in the example below.
>>> english, maths, physics, chemistry, computerSc = 80, 90, 85, 95, 90
>>> totalMarks = english + maths + physics + chemistry + computerSc
>>> print('english:', english, 'maths:', maths, 'physics:', physics, 'chemistry:',
chemistry, 'computer sc:', computerSc)
english: 80 maths: 90 physics: 85 chemistry: 95 computer sc: 90
>>> print('total marks:', totalMarks)
total marks: 440

Give one word answer to what each of the following is called:
1. Symbols used to separate various tokens in a statement.
2. Constant or a fixed value of a data type.
3. An identifier that denotes a data value in memory.
4. A function that gives the unique identity of an object.

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