Page 184 - Computer Science V2.0 Class 11

The execution of program 7.1 generates an error because input() returns a string value and the binary operation
multiplication cannot be performed on strings. So, execution of the statement, square = num * num, results in an
error. Of course, if the data type of the value being returned by input() is converted to an integer prior to assigning
it to num, using int(), then an arithmetic operation can be performed on num. The revised version of program 7.1
given below. It correctly displays the square of number 5 as output.

Program 7.2 Revision of program 7.1

01 # Objective: To accept a number and display its square.
02 num = int(input("Enter a number: ")) # explicit type conversion
03 square = num * num
04 print("The square of the entered number is", square)
Sample Output:
>>> Enter a number : 5
The square of the entered number is 25
Table 7.8 lists some of the functions that can be used for explicit type conversion in Python. In this table, the name
num denotes a numeric object.
Table 7.8: Functions for explicit type conversion in Python
Function Description

int(num) Converts num to an integer
float(num) Converts num to a floating-point number

str(num) Converts num to a string on which no arithmetic calculations can be done
chr(num) Converts num to str, if in suitable range

ord(character) Transforms an ASCII character to its ASCII code and a Unicode character to its Unicode.

7.9 Types of Errors

Various types of errors may be generated while creating or executing a program. The process of identifying and
removing such errors is known as debugging. The errors are called bugs. The errors in a program broadly fall in three
categories:
● Syntax Error ● Logical Errors ● Runtime Errors

7.9.1 Syntax Errors

Every programming language is described by a set of rules, collectively called the syntax of the language. If a program
violates a syntax rule, the interpreter/compiler will flash an error. Such errors are known as syntax errors. Thus, a Python
interpreter will execute only those statements that are syntactically correct. When a syntax error is encountered, the
execution of the program stops, and the error message is displayed. The execution of the program resumes only after
the error is rectified. For example,

>>> print("hello)
SyntaxError: incomplete input
in the statement print("hello), the closing quotation marks are missing, leading to a syntax error. Python
interpreter noted the beginning of string, but could not find the closing quotation marks. A syntax error must be
removed before Python interpreter can proceed.

Python Interpreter gives a brief description of each error, as seen in the above example.

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