Python Programming

Class 1

Author: Jose Miguel Arrieta R.

¿What is a Computer program?

¿What is Python?

Designed by Guido van Rossum

Python is a high-level programming language, and its core design philosophy is all about code readability and a syntax which allows programmers to express concepts in a few lines of code.”

Python Advantages

• Readable: Intuitive and strict syntax
• Productive: saves a lot of code.
• Portable: For every operating system.
• Reloaded: It comes with many libraries.

¿What is Python used for?

• Web Development
  • Frameworks such as Django, Flask
• Data Analysis
  • Libraries such as NumPy and Pandas
  • Data visualisation libraries like Matplotlib and Seaborn
• Internet Of Things
  • Raspberry Pi + python

• ​Web Scraping
  • Example: https://scrapy.org/

• Computer Vision

  • OpenCV library

• Machine Learning
  • Libraries such as Scikit-Learn, NLTK and TensorFlow.
• Game Development
  • PyGame

Programming tools

Download: https://www.anaconda.com/download/.

• Anaconda is the world’s most popular Python data science platform (Everything you need 'out of the box').
  • ​Includes: ​
    • Spyder (IDE/editor - like pycharm) and Jupyter

Spyder

Spyder is an  Integrated Development Environment (IDE).

Console

Spyder is the Scientific PYthon Development EnviRonment

Sublime is an text editor

Notes:

• When to use?
  • Reports with code
  • Reproducible  

The Jupyter Notebook is an open-source web application that allows you to create and share documents that contain live code, equations, visualizations and narrative text.

Example:  https://nbviewer.jupyter.org/github/waltherg/notebooks/blob/master/2013-12-03-Crank_Nicolson.ipynb

Python Code

Data Types

1. Conversions 
2. type command

• Integer <int>

• Float   <float>

• String  <str>

• Boolean <bool> 

• etc.

• Example

>>> type(5)
<type 'int'>

>>> type('str')
<type 'str'>

>>> type(4.6)
<type 'float'>

Variables

Variables are used to store information to be referenced and manipulated in a computer program.

• Example

a = 5.0
b = 'Hola'
c = 5+6

Math operators

• + plus
• - minus
• /   
• * multiply
• < less-than
• < greater-than
• <= less-than-equal
• >= greater-than-equal

• and
• or
• not

Logic operators 

Input/Output operators

Input and output (I/O) operators are used to take input and display output.

>>> a = input('Inserte un número: ')
Inserte un número: 3
>>> a
3
>>> print(a)
3
>>> print('Hola')
Hola

Comments

Single-line comments

Comments that span multiple lines

# This is a comment

"""
a = input('Inserte un número: ')
a
print(a)
print('Hola')
"""

print('This is not commented')

Exercise 1

1. Write a script that request two number from user
2. Make a sum with the two numbers and save result in a variable. 
3. Finally print result variable

• Note: Write script in Spyder, save, open console and run with python in console. 

Answer 1

#Sum Two numbers. 

# Request first number from user. 
a = float(input("Ingrese un numero: "))

# Request second number to user. 
b = float(input("Ingrese otro numero: "))

# Make the sum. 
c = a + b

# Show result in screen.
print("\nLa suma de los numeros es: " +str(c))

Exercise 2

• Create an algorithm to calculate perimeter and area of a circle

1. Create a variable with  pi value 
2. Request radio to the user 
3. Calculate perimeter and save in variable
4. Calculate area and save in variable 
5. Print in screen perimeter and area variables 

Answer 2

# Variables:
PI = 3.141592

# Request the radio to the user
r = float(input("Ingrese el radio del circulo: "))

# Calculate perimeter 
p = 2 * PI * r

# Calculate area
a = PI * r ** 2

# Muestra los resultados en pantalla
print "El perímetro del circulo es: ", p
print "El área del circulo es: ", a

Exercise 3

Algorithm to transform Fahrenheit to Celsius

1. Request Fahrenheit to user
2. Make transformation
3. Show result in screen

Answer 3

# Request Fahrenheit degrees to transform into Celsius
f = float(input("Ingrese los grados Fahrenheit:"));

# Make conversion 
c = (f - 32.0) * (5.0 / 9.0);

# Show result in screen 
print f, " grados Fahrenheit corresponden a ", c, " grados Centígrados"