Python - Module 1

Maria João Mira Paulo

Variables and built-in functions.

Why Python?

1. Python is a 'high-level language' ➡️ readable and easy to learn;

2. Python is an interpreted language. No need for a compiler.

2. Python is versatile:

       - Web Development,

       - Machine Learning,

       - Numeric Computing;

🤔

Installation

1. Pick version: Python 2 vs Python 3;

2. Python Installation Link: https://www.python.org/downloads/

3. Install IDE: https://code.visualstudio.com/

recommended

Just a tip 🧐

integrated development

environment

Check installation

✅

Python

So... Let's get started?

Variables

 ( name-value pairs ) 

Makes it possible to assign a value to a variable. 

Variable names may contain letters, numbers, and underscores, but must always begin using a letter. 
A single variable can take on multiple values over its lifetime without any problem. 

A single variable can take on multiple values over its lifetime without any

problem at all

Variables types

The basic types are:

- Int | whole numbers

- String | list of characteres
- Float | decimals
- Boolean | True or False
- Null | the absence of value

Strings

Varible value represents text.

Strings are always surronded by "" or ''. 

Let's try... 💻

If you want to use "", both as the delimiter and in the string, escape the quotation character by prepending it with a backslash (\).

Variable

Naming is very important.

- Don't make them too long
- Don't make them too short
- Make them descriptive
- They cannot have spaces 
- They must begin with letters or undescore '_'

There are non-python specific rules:

There are python specific rules:

- Use "snake case" when your variable is long enough to have more than one word. 
Example: a_varible_name instead of avariablename or aVariableName

Strings

Use the + sign to concatenate strings. 

Indexing

Each character in a string will be assigned an index.

y

p

t

h

o

n

1

0

2

3

4

5

Can you guess the value of language[3]? 

-5

-6

-4

-3

-2

-1

String Slicing

y

p

t

h

o

n

1

0

2

3

4

5

Numbers

Python supports both integers and float numbers.

Here, age is a integer ( variable type int) and weight is a float number, since it contains a decimal point(variable type float). 

Numeric operations: +, -, *, /, ** (exponentiate)  

Built-in Functions

But first ... What is a function? 

- Is a section of reusable code which performs an action;

- will always have:

       (mandatory) name

       (optional) receive arguments

       (optional) return data

Relax... These concepts will be clarified later 🤯

Built-in Functions

 - print(): receives an argument and displays that value on the screen.

- len(): receives a string and returns the length of that string.

Can you print the length of the word "python" on the screen? 

Let's try... 💻

Built-in Functions

 - input(): waits for someone to type at the keyboard, waits for input.

Let's try... 💻

Built-in Functions

 - str(): converts a number to a string.

 - int(): converts a string to an integer number

- float(): converts a string to a float number

Let's try... 💻

Built-in Functions

 - type(): returns variable type.

Let's try... 💻

String Methods

 - upper(): converts a string to upper case.

 - lower(): converts a string to lower case.

String Methods

https://panda.ime.usp.br/pensepy/static/pensepy/08-Strings/strings.html

Exercises

Ask for two number and return the value of the product of those two numbers. 

1.

Take two number and check whether the sum is greater than 5, less than 5 or equal to 5.

2.

Print the sum of the number of occurences of the character "a" and the number of occurences of the character "o" in the sentence: "Python 3 is awesome".

3.