data tyeps and variables in python

1. PYTHON PROGRAMMING WITH
WEB FRAMEWORKS – CSE304
This presentation contains the
concepts related to work with data
types and variables, numeric data,
string data

2. Data Types
• When you develop a Python program, you work with
variables that store data.
• A data type defines the type of data for a value.
• 3 types of basic Python data types:
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3. 3

4. Data Types
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5. Data Types
• How to code literal values (there are two literals)
– String literal (enclose the characters of the string in
single or double quotation marks).
– Numeric literal (code the number without quotation
marks).
• You can assign a value of any data type to a variable.
• An assignment statement uses the equals sign (=) to
assign a value to a variable.
• The value can be a literal value, another variable, or
an expression like the arithmetic expressions.
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6. Variables
• A Python variable is a symbolic name that is a
reference or pointer to an object.
• Once an object is assigned to a variable, you can refer
to the object by that name anywhere inside the
program.
• How to name variables ?
– Give meaningful names. That means that it should be
easy to tell and easy to remember.
– Avoid abbreviations.
– Use underscore notation. (example: tax_rate)
– You may use camel case. (example: taxRate)
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7. Rules for naming variables
• A variable name must begin with a letter or
underscore.
• A variable name can't contain spaces, punctuation,
or special characters other than the underscore.
• A variable name can't begin with a number, but can
use numbers later in the name.
• A variable name can't be the same as a keyword
that's reserved by Python.
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8. Python Keywords
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9. Python 3.9.X Keywords List
• 36 keywords
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10. Python's arithmetic operators
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11. How to work with numeric data
• The order of precedence for arithmetic expressions:
• Examples that show the order of precedence and use
of parentheses
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12. How to work with numeric data
• An arithmetic expression consists of one or more
operands that are operated upon by arithmetic
operators.
• No need of spaces before and after the arithmetic
operators.
• When an expression mixes integer and floating-point
numbers, Python converts the integers to floating-
point numbers.
• Use parentheses to clarify the sequence of
operations (when multiple operators are used).
Otherwise, Python applies its order of precedence.
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13. How to work with numeric data
• Compound assignment operators provide a
shorthand way to code common assignment
statements.
• Besides the compound operators in the table. Python
offers /=. //=. %=, and **=.
• When working with floating-point numbers, be aware
that they are approximations, not exact values. This
can cause inaccurate results.
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14. Other Operators
• Comparison Operators:
!=, ==, <, <=, >, >=
• Unary Operators:
Unary plus (+)
Unary minus (-)
• Bitwise Operators
&(AND), |(OR), ^(XOR), ~(One's Compliment),
<< (Left Shift), >>(Right Shift)
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15. Other Operators
• Logical Operators:
and, or, not
• Assignment Operators:
=, +=, -+, *=, /=, //=,...
• Membership Operators:
in, not in
• Identity Operators:
is , is not
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16. Operator Precedence
• Parenthesis – ()
• Exponentiation – **
• Compliment, unary plus and minus – ~, +, -
• Multiply, Divide, modulo – *, /, %
• Addition and Subtraction – +, -
• Right and Left Shift – >>, <<
• Bitwise AND – &
• Bitwise OR and XOR – |, ^
• Comparison Operators – ==, !=, >, <, >=, <=
• Assignment Operator- =
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17. How to use the interactive shell for testing
numeric operations
• Demo
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18. How to work with string data
• You can also create an empty string by coding a set of
quotation marks with nothing between them.
• And you can assign a new value to a string variable.
This works the same way it does with numeric
variables.
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19. How to work with string data
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20. Common escape sequences
• you can use escape sequences to include certain
types of special characters such as new lines and tabs.
• You can also use escape characters to include special
characters such as quotation marks and backslashes.
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21. Common escape sequences
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22. Common escape sequences
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