Python Fundamentals for the begginers in programming

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2 Python Fundamentals
Course: PROG12583

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Objectives
At the end of this module, students will be able to:
• Define the fundamentals of computer programming with Python
language.
• Analyze code syntax.
• Apply the programming fundamentals by writing python programs using
the IDE (Visual Studio Code).
• Identify different types of errors in a program and fix them.
• Define and analyze numbers and arithmetic expressions through code.
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Part - 1

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Block of statements:
• A statement in Python is the instructions you type in the editor (visual
studio code) that interpreter executes, e.g., print(“Hello World!”). Python
interpreter executes the print statement and displays the result to the
console.
• A block is a group of statements in a program or script. Usually, it
consists of at least one statement and of declarations for the block,
depending on the programming or scripting language. Your code could
also contain nested blocks.
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Block of statements: an example of a block of statement (lines 3 and 4)
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Rules for coding Python
• Python relies on proper indentation.
• Unlike many programming languages, the indentation of each line
matters in a Python program. With Python, the indentation is typically
four spaces (or one tab).
• Python doesn't use braces { } to indicate blocks of code for class and
function definitions or flow control.
• Blocks of code are denoted by line indentation, which is rigidly
enforced. All statements within the block must be indented the same
amount.
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Indentation Examples:
• A good indentation in Python:
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Indentation Examples:
• An indentation that causes an error:
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Statement continuation:
• You can use implicit continuation.
• To do that, you divide a statement before or after an operator like a plus
or minus sign.
• You can also divide a statement after an opening parenthesis.
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Statement continuation:
• You can also use explicit continuation.
• To do that, you code a backslash to show that a line is continued.
• However, this way is discouraged.
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Comments:
• Adding comments to programs is a very important practice in
programming.
• Comments are added for people (not the computer) to understand what
a part of the program does – they are notes added by programmers to
explain part for the code.
• Python interpreter ignores the comments – it does not execute them.
They have no effect on the operation of the program.
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Comments:
• To add a comment to describe a portion of the code, type # then type
the python statement.
• You can also add a comment after the statement (inline comments).
• Another way to add a comment is by commenting out a python
statement, if you don’t want the interpreter to execute that statement
(this is mainly for testing purpose).
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Comment examples:
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Quotation in Python:
• In programming terms, a sequence of characters that is used as data is
called a string.
• When a string appears in the actual code of a program, it is called a
string literal.
• In Python code, string literals must be enclosed in quote marks.
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• Python accepts single ('), double (") and triple (''' or """) quotes to
denote string literals, as long as the same type of quote starts and ends
the string.
• The triple quotes are used to span the string across multiple lines. In
this case, the string can be a comment.
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• The quote marks are not displayed when the statement executes.
• The quote marks simply specify the beginning and the end of the text
that you wish to display.
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output

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• If you want a string literal to contain either a single-quote or an
apostrophe as part of the string, you can enclose the string literal in
double-quote marks.
• Likewise, you can use single-quote marks to enclose a string literal that
contains double-quotes as part of the string.
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output

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Working with datatypes and variables in Python:
• We saw three different types of data in the previous examples – string
(str), integer (int) and floating-point (float).
• The str data type holds string literals.
• The int and float data types hold numerical literals.
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• When you develop a python program, you work with variables that store
data (values). Variables vary as code executes.
• To work with variables, you assign data to them using the assignment
operator (=). This is called (assignment statement).
• Initialization is when assign an initial value to a variable. Then different
values are assigned later in the program.
• You can assign literal values or literal strings to a variables.
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Working with datatypes and
variables in Python:
• To code a literal value for a string,
enclose the characters of the string
in single or double quotation
marks. This is called a string literal.
• To code a literal value for a
number, code the number without
quotation marks. This is called a
numeric literal.
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Working with datatypes and
variables in Python:
• You can also assign multiple
values to multiple variables in one
statement.
• Because variable names are
case-sensitive, you must be sure
to use the correct case when
coding the names of variables.
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Variables naming conventions that must be respected by programmers
• 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.
• Use underscore notation or camel case.
• Use meaningful names that are easy to remember.
• Don’t use the names of built-in functions, such as print().
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Variables naming conventions
A variable name can’t be the same as a keyword that’s reserved by Python.
Two naming styles for variables
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The print() function:
• The print function is one of the most important built-in functions in
python that you will be using to print out and display the results
(outputs) of the code to the screen.
• A function is a reusable unit of code that performs a specific task.
• Python provides many built-in functions that do common tasks like
getting input data from the user and printing output data to the console.
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• When you call a function, you code the name of the
function followed by a pair of parentheses.
• Within the parentheses, you code any arguments
(could values of variables) that the function requires,
and you separate multiple arguments with commas.
• In a syntax summary like the one at the top of this
page, brackets [ ] mark the portions of code that are
optional.
• The italicized portions of the summary are the ones that
you have to supply.
• But note that the arguments are optional. If no
arguments are passed to this function, it prints a blank
line.

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• Print can take other arguments like (sep)
and (end).
• sep: string inserted between values,
default a space.
• end: string appended after the last value,
default a newline.

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The type() function:
• type() is another built-in function that can
be used by programmers to debug their
code( debugging is the process of
identifying and fixing bugs in the software).
• It returns the class type of object (data)
passed to it, in between the parenthesis.
• The example, on the right, shows the data
type of list (line 1), tuple (line 2), string (line
3), float (line 4) and integer (line 5).
• We will discuss more of the data types
later.

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Type casting (conversions):
• There are two types of type conversion in
python; implicit and explicit type
conversions.
• In the implicit, python automatically
converts one data type to another.
• Python can perform the conversion of
lower datatypes to the higher without data
loss like converting integer to float.

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• In the explicit, programmers perform the conversion using some pre-defined functions
(e.g., int(), float(), str()).
• The int() converts numbers with decimals (e.g., 89.5) or literal values in between quotes (
‘123’) into integer.
• The float() converts integers to float format (adding a zero after the decimal point) or literal
values in between quotes into float.
• You cannot convert string literal into numbers (e.g., “abc” into a number).
• The str() converts values into strings (e.g., 87 into “87”).

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Types of errors:
• As you test your program, three types of errors can occur.
• Syntax errors prevent your program from compiling and running. Since syntax
errors occur when Python attempts to compile a program, they’re known as
compile-time errors. This type of error is the easiest to find and fix.
• When you use Visual Studio Code, it highlights the location of the syntax errors
that it finds each time you attempt to run the program. Then, you can correct that
error and try again.

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Types of errors:
Common syntax errors
• Misspelling keywords.
• Forgetting the colon at the end of the opening line of a function definition, if clause,
else clause, while statement, for statement, try clause, or except clause.
• Forgetting an opening or closing quotation mark or parenthesis.
• Using parentheses when you should be using brackets, or vice versa.
• Improper indentation.

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Types of errors:
• Syntax error example (can you figure what causes theses errors?!)

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Types of errors:
• Runtime errors don’t violate the syntax rules, but
they throw exceptions (errors that python
interpreter generates and displayed in the
console or the terminal) that stop the execution of
the program. Many of these exceptions are due to
programming errors that need to be fixed.
• This example shows the runtime error occurs
when trying to divide a value by zero. You notice
that there was no syntax error meaning the
program was compiled and run and then python
threw an exception: ZeroDivisionError: division by zero

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Types of errors:
• Logic errors are statements that don’t cause syntax or runtime errors, but produce
the wrong results. In the example shown above the program produced a wrong
result. The value of average should be 90, not 260.
• It is the programmer’s responsibility to ensure that the code is written right so the
result is right.
• (can you try and fix the error ?!!)

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Class exercises: Do it yourself !
Write a python program to produce the following output (define variables
and assign values to them, then use print function).

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Write a python program that contains 4 variables for 4 grades of a
student. Assign values to the variables. Find the sum of the 4 grades.
Make sure to use explicit continuation for the sum statement. Print the
sum and use the end keyword in the print statement. Your program should
start with a comment that spans two lines to describe your code.

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Write a python program that assign 3 tax amounts to 3 variables all in one
statement. Then print all the values using one print statement with the sep
keyword.

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Working with numeric data
and arithmetic operations
Part - 2

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• Arithmetic operators consist of two or more
operands that are operated upon by arithmetic
operators.
• The operands in an expression can be either
numeric variables or numeric literals.
• The +, -, * and / are the same as those used in
basic arithmetic.
• Python also has an operator for integer division (//)
that truncates the decimal portion of the division. It
has a modulo operator (%), or remainder operator,
that returns the remainder of a division. And it has
an exponentiation operator (**) that raises a number
to the specified power.

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• The order of precedence: when an expression
includes two or more operators, the order of
precedence determines which operators are applied
first. This order is summarized in the table in this
figure. For instance, Python performs all
multiplication and division operations from left to
right before it performs any addition and subtraction
operations.
• If you need to override the default order of
precedence, you can use parentheses. Then,
Python performs the expressions in the innermost
sets of parentheses first, followed by the
expressions in the next sets of parentheses, and so
on.

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• On the right side:
Code that calculates sales tax
Code that calculates the perimeter
of a rectangle

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• The compound assignment(=) operators provide a shorthand way to code common
assignment statements.
• For instance, the += operator modifies the value of the variable on the left of the
operator by adding the value of the expression on the right to the value of the variable
on the left. When you use this operator, the variable on the left must already have
been initialized.
• The other operators, -= and *= work similarly.

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Floating-point numbers:
• A floating-point number consists of a positive or negative sign, a decimal value for the
significant digits, and an optional exponent.
• Floating-point numbers provide for very large and very small numbers, but with a
limited number of significant digits. The float type can only use 16 significant digits to
store the number.
• To express the value of a floating-point number, you can use scientific notation.
• This notation consists of an optional plus sign or a required minus sign, a decimal
value for the significant digits, the letter e or E, and a positive or negative exponent.
For example:
2.302e+5

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• In this example, the number contains four significant digits (2.302), and the exponent
specifies how many places the decimal point should be moved to the right or to the
left. Here, the exponent is positive so the point is moved to the right and the value is:
230,200
• But if the exponent was negative (e-5), the point would be moved to the left and the
value would be:
.00002302
• An integer is an exact value that yields expected results.
• A floating-point number is an approximate value that can yield unexpected results
known as floating-point errors.

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• The floating-point numbers are approximate values,
not exact values. Look at this example:
• In this example, Balance should be 300.30
• As a result, they sometimes cause floating-point errors.
• To fix this error, we use round() function. The round()
function can take additional argument which is an integer
that represents the number of digits to display after the
decimal point.

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The standard math module:
• The math module for Python provides many functions
for mathematical, trigonometric, and logarithmic operations.
• The floating-point numbers are approximate values,
not exact values. Look at this example:
Balance should be 300.30
• As a result, they sometimes cause floating-point errors.
• To fix this error, we use round() function. The round()
function can take additional argument which is an integer
that represents the number of digits to display after the
decimal point.

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• We list four common functions and the pi constant that required importing the math
module.
• You can use the ceil() function if you always want to round up (towards the ceiling).
And you can use the floor() function if you always want to round down (towards the
floor). See examples in next slide
* you can also use the exponential operator (**) to raise a number to the power.

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• The m in the import statement is called alias that is defined so we use through
the program instead of using the module name – math.

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• The m in the import statement is called alias that is
defined so we use through the program instead of
using the module name – math.

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• Create a program that calculates a user’s weekly gross and take-home pay.
• Follow the Console (on the right) and assign values to the hours Worked and hourly pay rate.
Specifications
The formula for calculating gross pay is:
 gross pay = hours worked * hourly rate
The formula for calculating tax amount is:
 tax amount = gross pay * (tax rate / 100)
The formula for calculating take home pay is:
 take home pay = gross pay – tax amount
• The tax rate should be 18%, but the program should store the tax rate in a variable so
you can easily change the tax rate later just by changing the value that’s stored in the variable.
Console
Pay Check Calculator
Hours Worked: 35
Hourly Pay Rate: 14.50
Gross Pay: 507.5
Tax Rate: 18%
Tax Amount: 91.35
Take Home Pay: 416.15

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• Create a program that calculates total sales and dsplays the following information to the
console.
• Follow the Console (on the right) and assign values to the cost of the meal and the tip percent.
Specifications
The formula for calculating the tip amount is:
 tip = cost of meal * (tip percent / 100)
Console
Tip Calculator
Cost of meal: 52.31
Tip percent: 20
Tip amount: 10.46
Total amount: 62.77

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• Create a program that converts the temperature in Celsius into Fahrenheit and vice versa.
• Follow the Console (on the right) and assign values to the cost of the meal and the tip percent.
Specifications
The formula for calculating the tip amount is:
 Fahrenheit = (Celsius * 9/5) + 32
 Celsius = (Fahrenheit – 32) * 5/9
Console
Temperature conversion Calculator
In Celsius: 20.0
In Fahrenheit: 68.0
In Fahrenheit: 68.0
In Celsius: 20.0

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Material has been taken from (can be accessed through Sheridan's Library Services) :
• Starting Out with Python (ISBN-13: 9780136912330 ):
• https://www.pearson.com/en-ca/subject-catalog/p/starting-out-with-
python/P200000003356/9780136912330
• Murach’s Python 2nd Edition programming, 2nd Edition :
• https://bookshelf.vitalsource.com/reader/books/9781943872756/pages/recent
• Introducing Python, Lubanovic, B., O'Reily Media, 2nd Edition, 2019
• https://www.oreilly.com/library/view/introducing-python-
2nd/9781492051374/
References

Python Fundamentals for the begginers in programming

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