In this post we will go through some basic python objects.

Type of Objects

Object to refer to any entity in a python program.
Python has some standard built in object types
- Numbers
- Strings
- Lists
- Tuples
- Dictionaries
Having a good knowledge on these basic objects is essential to fee comfortable in Python programming.

Numbers

Numbers: integers & floats

In [39]:

age=30
age

Out[39]:

In [34]:

weight=102.88
weight

Out[34]:

102.88

In [35]:

x=17
x**2 #Square of x

Out[35]:

Check the variable types for age and weight in variable explorer

In [37]:

type(age)

Out[37]:

int

In [38]:

type(weight)

Out[38]:

float

Strings

Strings are amongst the most popular types in Python. There are a number of methods or built-in string functions

Defining Strings

In [40]:

name="Sheldon"
msg="Data Vedi Data Science Classes"

Accessing strings

In [41]:

print(name[0])
print(name[1])

S
h

This is as good as substring

In [42]:

print(msg[0:9])

Data Vedi

length of string

In [44]:

len(msg)

Out[44]:

In [43]:

print(msg[10:len(msg)])

Data Science Classes

Displaying string multiple time

In [45]:

msg="Site under Construction"
msg*10
msg*50

Out[45]:

'Site under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under ConstructionSite under Construction'

There is a difference between print and just displaying a variable.

In [47]:

message="Data Science on R and Data Science on Python \n"
message*10

Out[47]:

'Data Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \nData Science on R and Data Science on Python \n'

In [46]:

print(message*10)

Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python 
Data Science on R and Data Science on Python

String Concatenation

In [48]:

msg1="Site under Construction "
msg2=msg1+"Go to home page \n"
print(msg2)
print(msg2*10)

Site under Construction Go to home page 

Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page 
Site under Construction Go to home page

List

List is a hybrid datatype
A sequence of related data
Similar to array, but all the elements need not be of same type

Creating a list

In [50]:

mylist1=['Sheldon','Male', 25]

Accessing list elements

In [52]:

mylist1[0] #Python indexing starts from 1

Out[52]:

'Sheldon'

In [53]:

mylist1[1]

Out[53]:

'Male'

In [54]:

mylist1[2]

Out[54]:

Appending to a list

In [55]:

mylist2=['L.A','No 173', "CR108877"]
final_list=mylist1+mylist2
final_list

Out[55]:

['Sheldon', 'Male', 25, 'L.A', 'No 173', 'CR108877']

Updating list elements

In [56]:

final_list[2]=35
final_list

Out[56]:

['Sheldon', 'Male', 35, 'L.A', 'No 173', 'CR108877']

Length of list

In [57]:

len(final_list)

Out[57]:

Deleting an element in list

In [58]:

del final_list[5]
final_list

Out[58]:

['Sheldon', 'Male', 35, 'L.A', 'No 173']

Tuples

Also sequence data types.
Crated using parenthesis. Lists were created using square brackets.
Tuples can’t be updated.

Tuples example:

In [60]:

my_tuple=('Mark','Male', 55)
my_tuple

Out[60]:

('Mark', 'Male', 55)

In [62]:

my_tuple[1]

Out[62]:

'Male'

In [63]:

my_tuple[2]

Out[63]:

In [61]:

my_tuple[0]*10

Out[61]:

'MarkMarkMarkMarkMarkMarkMarkMarkMarkMark'

Difference between tuples and lists

In [65]:

my_list=['Sheldon','Male', 25]
my_tuple=('Mark','M', 55)

my_list[2]=30
my_list

Out[65]:

['Sheldon', 'Male', 30]

In [68]:

my_tuple[2]=40

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-68-c6d510f4ba89> in <module>()
----> 1 my_tuple[2]=40

TypeError: 'tuple' object does not support item assignment

Dictionaries

Dictionaries have two major element types key and Value.
Dictionaries are collection of key value pairs
Each key is separated from its value by a colon (:), the items are separated by commas, and the whole thing is enclosed in curly braces.
Keys are unique within a dictionary

In [71]:

city={0:"LA", 1:"PA" , 2:"FL"}
city

Out[71]:

{0: 'LA', 1: 'PA', 2: 'FL'}

In [72]:

city[0]

Out[72]:

'LA'

In [73]:

city[1]

Out[73]:

'PA'

In [70]:

city[2]

Out[70]:

'FL'

In dictionary, keys are similar to indexes. We define our own preferred indexes in dictionaries.
Make sure that we give the right key index while accessing the elements in dictionary.

In [74]:

names={1:"David", 6:"Bill", 9:"Jim"}
names

Out[74]:

{1: 'David', 6: 'Bill', 9: 'Jim'}

In [82]:

names[0] #Doesn't work, because we haven't assign "0" to any value?

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-82-2bdf624c7c2b> in <module>()
----> 1 names[0] #Doesn't work, because we haven't assign "0" to any value?

KeyError: 0

In [77]:

names[1]

Out[77]:

'David'

In [79]:

names[2]

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-79-5fc2e5d7f092> in <module>()
----> 1 names[2]

KeyError: 2

In [80]:

names[6]

Out[80]:

'Bill'

In [81]:

names[9]

Out[81]:

'Jim'

In the key value pairs, key doesn’t always need to be a number.

In [83]:

edu={"David":"Bsc", "Bill":"Msc", "Jim":"Phd"}
edu

Out[83]:

{'Bill': 'Msc', 'David': 'Bsc', 'Jim': 'Phd'}

In [86]:

edu[0]

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-86-097da42662a8> in <module>()
----> 1 edu[0]

KeyError: 0

In [87]:

edu[1]

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-87-86fe0fd73d3a> in <module>()
----> 1 edu[1]

KeyError: 1

In [88]:

edu[David]

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-88-9c7944aa3a3d> in <module>()
----> 1 edu[David]

NameError: name 'David' is not defined

In [89]:

edu["David"]

Out[89]:

'Bsc'

Updating values in dictionary

In [90]:

edu

Out[90]:

{'Bill': 'Msc', 'David': 'Bsc', 'Jim': 'Phd'}

In [91]:

edu["David"]="MSc"
edu

Out[91]:

{'Bill': 'Msc', 'David': 'MSc', 'Jim': 'Phd'}

Updating keys in dictionary.
Delete the key and value element first and then add new element.

In [94]:

city={0:"LA", 1:"PA" , 2:"FL"}
#How to make 6 as "LA"
del city[0]
city

Out[94]:

{1: 'PA', 2: 'FL'}

In [93]:

city[6]="LA"
city

Out[93]:

{1: 'PA', 2: 'FL', 6: 'LA'}

Fetch all keys and all values separately

In [96]:

city.keys()

Out[96]:

dict_keys([1, 2])

In [95]:

city.values()

Out[95]:

dict_values(['PA', 'FL'])

In [97]:

edu.keys()

Out[97]:

dict_keys(['Jim', 'Bill', 'David'])

In [98]:

edu.values()

Out[98]:

dict_values(['Phd', 'Msc', 'MSc'])

104.1.3 Python Objects

Quick look into python objects.

Type of Objects

Numbers

Strings

List

Tuples

Dictionaries

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104.1.3 Python Objects

Quick look into python objects.

Type of Objects

Numbers

Strings

List

Tuples

Dictionaries

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