Page 170 - Computer Science Class 11 Without Functions
P. 170
Ø type() is used to get the data type of an object.
Ø A Python sequence is an ordered collection of items. Each item in a sequence is indexed by an integer.
Ø Strings (str), lists (list), and tuples (tuple) are examples of sequence types.
Ø A string is a sequence of characters enclosed in single (') or double (") quotation marks.
Ø A string enclosed between single or double quotation marks is usually restricted to one line, but a longer
string may be continued on next line by terminating the line with a backslash character. For example,
>>> 'Hello,\
… How are you?'
'Hello,How are you?'
Ø A list is a sequence of objects (possibly heterogeneous) enclosed in square brackets: [].
Ø A tuple is a sequence of objects (possibly heterogeneous) enclosed in parenthesis ().
Ø A set is an unordered and unindexed collection of data items separated by a comma enclosed in curly
brackets {}.
Ø The type NoneType has only one member, namely, None.
Ø A dictionary is an unordered set of key-value pairs enclosed in curly brackets {}.
Ø Numeric data types (int, float, and complex), bool, str, and tuple are immutable data types.
Ø Lists and dictionaries are mutable data types.
Ø Operators are used to perform an operation on the values, called operands.
Ø A unary operator requires only one operand, while a binary operator requires two operands.
Ø The arithmetic operators are used to perform arithmetic operations: addition (+), subtraction(-),
multiplication(*), division(/, %,//), and exponentiation(**).
Ø Assignment operators are used to assign the value of the operand on the right-hand side of the assignment
operator to the operand on the left-hand side of the operator.
Ø There are three logical operators: not, and, or.
Ø Identity operators are used for checking the data type of a variable.
Ø There are two identity operators: is and is not.
Ø Membership operators are used to check whether a particular value is a member of a given string, list, tuple,
set, or dictionary. A membership operation yields True or False.
Ø An expression in Python is defined as a valid combination of objects and operators.
Ø When an expression contains multiple operators, Python resolves the order of execution according to
precedence of operators.
Ø Type conversion is the process of converting the value of one data type to another.
Ø Implicit type conversion, also known as coercion, takes place when a data value is converted from one data
type to another by the Python interpreter, without explicit type conversion by the programmer. For example,
3+4.6 yields a floating point number.
Ø Explicit conversion, also called typecasting, takes place when a programmer gives such an instruction. For
example, int(7.4).
Ø If the rules of a programming language are not followed, the interpreter/compiler will flash an error. Such
errors are known as syntax errors.
Ø A program free from syntax errors may still contain logical errors leading to erroneous output.
Ø The process of identifying and removing logical errors is known as debugging.
Ø A runtime error may occur during the execution of the program.
168 Touchpad Computer Science-XI

