Introduction to Python - Algorithm Compiler

Little Intro
❏ Raza Ul Mustafa, PhD - Computer Engineering
❏ Research areas: NLP, Video, Quality of Experience, Quality
of Service, Machine & Deep Learning
❏ Publications - 20 + → Languages used in my papers:
Python :)
❏ Main Courses of Interests: Programming
❏ Python, Web-programming, C/C++, Linux
❏ Worked & Working on Research Projects: 3+

Books
- The primary text for this course is a freely available online textbook called
Think Python: How to Think like a Computer Scientist.
- We will be using the interactive version of the text that is available through
Runestone Academy at https://runestone.academy.

Outline of course - Main topics
1. Variables & Operations
2. Strings & Numbers
3. Functions
4. Conditions / If/Elif/Else
5. Iterations – Very Important
6. Lists, Dictionaries, Tuples – Important in Python
7. Recursion, Sorting
8. OOP – Very important in all languages

Software to Install
- Anaconda & Spyder
Windows Installation -
https://docs.anaconda.com/free/anaconda/install/win
dows/
Mac Installation -
https://docs.anaconda.com/free/anaconda/install/mac
-os/
Linux -
https://docs.anaconda.com/free/anaconda/install/linu
x/

First program
print("Hello, World!")

The way of program
❏ The single most important skill for a computer scientist is problem solving
❏ A program is a sequence of instructions that speciﬁes how to perform a
computation.

Algorithms
- If problem solving is a central part of computer science, then the solutions that
you create through the problem solving process are also important.
- In computer science, we refer to these solutions as algorithms.
- An algorithm is a step by step list of instructions that if followed exactly will
solve the problem under consideration.
Our goal in computer science is to take a problem and develop
an algorithm that can serve as a general solution

The python programming languages
Python is an example of a high-level language; other high-level
languages you might have heard of are C++, PHP, and Java.
High Level Languages: They are very easy to understand, i.e.,
resembles natural language or mathematical notation and is
designed to reﬂect the requirements of a problem
Low Level Languages: They are also called machine-level
languages. 0101

Advantages of high level languages
- First, it is much easier to program in a high-level language.
- Programs written in a high-level language take less time to
write, they are shorter and easier to read, and they are
more likely to be correct.
- High-level languages are portable, meaning that they can
run on different kinds of computers with few or no
modiﬁcations.

Then who process the codes?
Two kinds of programs process high-level languages into
low-level languages: interpreters and compilers.
- Interpreters: An interpreter reads a high-level program and
executes it, meaning that it does what the program says.
- Compiler: A compiler reads the program and translates it
completely before the program starts running.
- In this case, the high-level program is called the source code, and the
translated program is called the object code or the executable.

Python Interpreter (1/2)
There are two ways to use the Python interpreter: shell mode and
program mode.
In shell mode, you type Python expressions into the Python shell, and the
interpreter immediately shows the result. The example below shows the
Python shell at work.

Python Interpreter (2/2)
Program mode: Alternatively, you can write an entire
program by placing lines of Python instructions in a file and
then use the interpreter to execute the contents of the file as
a whole. Such a file is often referred to as source code.

Saving and extension
By convention, ﬁles that contain Python programs
have names that end with .py.
Following this convention will help your operating
system and other programs identify a ﬁle as
containing python code.

What is debugging
Programming is a complex process. Since it is done by human
beings, errors may often occur.
Programming errors are called bugs and the process of tracking
them down and correcting them is called debugging.
● syntax errors,
● runtime errors,
● semantic errors.

Syntax errors
Python can only execute a program if the program is
syntactically correct; otherwise, the process fails and returns
an error message.
Syntax refers to the structure of a program and the rules
about that structure
Example – Next slide

Runtime errors
❏ The second type of error is a runtime error, so called
because the error does not appear until you run the
program.
❏ These errors are also called exceptions because they usually
indicate that something exceptional (and bad) has happened.

Semantic errors
- The third type of error is the semantic error.
- If there is a semantic error in your program, it will run
successfully in the sense that the computer will not generate
any error messages.
- However, your program will not do the right thing. It will
do something else. Speciﬁcally, it will do what you told it to
do.

Experimental debugging
One of the most important skills you will acquire is debugging.
Although it can be frustrating, debugging is one of the most
intellectually rich, challenging, and interesting parts of
programming.
Advice: Visualize

Comments in python
A comment in a computer program is text that is intended only for
the human reader - it is completely ignored by the interpreter. In
Python, the # token starts a comment. The rest of the line is
ignored. Here is a new version of Hello, World!.

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Introduction to Python - Algorithm Compiler

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