

In [ ]:

    
%matplotlib inline

Python Basics

Objectives:

Overview "things"
- comments
- data types
- variables
- Containers (i.e. Lists and Dictionaries)
Overview how to do "Actions"
- Functions
- Methods

In Python, you have "things" and "actions".

_{Now, these are my own made-up terms that I'll use for now just to make things simple. In reality, Python uses the term "Objects" for what I call "things", and... well, I don't think Python has a term for what I call "actions", but for now none of this matters... lets start:}

"Things"

Comments

Before you to write "code", you need to learn how to write "comments", which are "text for humans" (as opposed to "Text for computers).

In Python, you simply add a # to indicate that the line is a comment:



In [ ]:

    
# this is a comment

Data types (i.e. raw materials)

Integers

Integers are used to represent "whole numbers" (i.e. no decimal point)



In [372]:

    
2 + 4









    Out[372]:





6

Strings

Strings are used to represent "letters"



In [373]:

    
'2' + '4'









    Out[373]:





'24'

Floats

Floats are used to represent "numbers with decimals"



In [374]:

    
2.5 + 4.1









    Out[374]:





6.6

There are more "Data types", but we can do a lot just with these ones above.

Variables (i.e. "Labels")

Variables are use to "name" or "label" things. Much like sticking a label on a jar and writing on the label: "sugar"

Lets "name" some floats



In [375]:

    
a = 1.2
b = 3.0
c = a + b

print c

4.2

Now lets "name" some strings



In [376]:

    
a = '1.2'
b = '3.0'
c = a + b

print c

Now lets introduce one more Data Type (Boolean), which is used to represent "True" or "False". Lets "name" some booleans



In [377]:

    
a = True
b = False

print a









    



True

Containers

"Containers" are "things" that are used to store other "things". Kinda' like storing your sugar in a jar...

Here are some of the more common "containers".

Lists

A "List" is a container specifically disigned to store... well, lists of "things".



In [378]:

    
mylist = ['a','b','c','d']

mylist









    Out[378]:





['a', 'b', 'c', 'd']



In [379]:

    
mylist[0]









    Out[379]:





'a'



In [380]:

    
mylist[-1]









    Out[380]:





'd'



In [381]:

    
mylist[1:4]









    Out[381]:





['b', 'c', 'd']

Dictionaries

A "Dictionary" is a container specifically disigned to store "things", in a way that resembles a dictionary. You look up the "key" word (e.g. "apple") and your immediatly get the contents (i.e. "Red round fruit that tastes good").

The idea of having a "key" word, is so that you don't have to scall the whole list to find what you want.



In [ ]:

    
myd = {'name':'Joe','age':25,'gender':'male'}

myd



In [ ]:

    
myd['name']



In [ ]:

    
myd['age']

"Things" within "things"...

Lets do a harder example:



In [382]:

    
myComplexThing = [{'name':'Joe','tickets':[2,5,7]},{'name':'Pepe','tickets':[1,6,9]},{'name':'Maria','tickets':[0,4,8]}]



In [383]:

    
myComplexThing[0]









    Out[383]:





{'name': 'Joe', 'tickets': [2, 5, 7]}



In [384]:

    
myComplexThing[1]['name']









    Out[384]:





'Pepe'



In [385]:

    
myComplexThing[2]['tickets'][-1]









    Out[385]:





8

"Actions"

1. Functions

Functions are used following the "nomenclature" below:

output = FunctionName(inputs)

For example, lets do a list... and then apply some functions to it.



In [386]:

    
mylist = [1,8,5,9]

print mylist









    



[1, 8, 5, 9]



In [387]:

    
type(mylist)









    Out[387]:





list



In [388]:

    
min(mylist)









    Out[388]:





1



In [389]:

    
a = max(mylist)

a









    Out[389]:





9



In [390]:

    
sum(mylist)









    Out[390]:





23



In [391]:

    
len(mylist)









    Out[391]:





4

Here is a list of the basic Functions built-in within Python:

https://docs.python.org/2/library/functions.html

However, there are a lot more. You can import functions from additional "modules" (or "packages")... therefore you have thousands of functions at your disposal. Here is an example about how to import a Module and use one of its functions.



In [392]:

    
# First import the module "math"
import math

# Then use the function "sin" within the module "math"
math.sin(mylist[0])









    Out[392]:





0.8414709848078965

Finally, you can also make your own function:



In [393]:

    
def my_cool_function(inputs):
    '''
    Here you add some instructions and examples
    '''
    output = sum(inputs)/2
    
    return output

Now that we made our own function... we can use it!



In [394]:

    
answer = my_cool_function(mylist)

print answer

2. Methods

Methods are similar to functions, but the follow a different "nomenclature":

output = input.MethodName(arguments)

For example...



In [395]:

    
mylist.append(2)

print mylist









    



[1, 8, 5, 9, 2]



In [396]:

    
mylist.remove(1)

print mylist









    



[8, 5, 9, 2]



In [397]:

    
mylist.sort()

print mylist









    



[2, 5, 8, 9]



In [398]:

    
mylist.index(5)









    Out[398]:





1

I bet, up to here, everything sound good and easy, but not really that useful.



In [400]:

    
# Import Pandas module
import pandas as pd

# Define URL of LOBO buoy
URL = 'http://lobo.satlantic.com/cgi-data/nph-data.cgi?min_date=20090610&max_date=20090620&y=temperature'

# Read data from LOBO buoy
mycoolvar = pd.read_csv(URL,sep='\t')

# Do quick plot
mycoolvar.plot();



In [ ]: