Learning Python from 0 in 30 minutes

1. Python in 30 minutes!*
Fariz Darari
* Recommended slide reading time unless otherwise specified

2. 2
Not this python, unfortunately

3. 3
But this Python!

4. 4
But this Python!
Programming Language

5. 5
But this Python!
Programming Language
Created in 1991 by Guido van Rossum

6. 6
But this Python!
Cross Platform
Programming Language
Created in 1991 by Guido van Rossum

7. 7
But this Python!
Programming Language
Freely Usable Even for Commercial UseCreated in 1991 by Guido van Rossum
Cross Platform

8. "Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
8
print("Python" + " is " + "cool!")

9. print("Python" + " is " + "cool!")
"Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
9

10. print("Python" + " is " + "cool!")
"Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
10
public class Main {
public static void main(String[] args) {
System.out.println("Hello world!");
}
}

11. print("Python" + " is " + "cool!")
"Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
11
public class Main {
public static void main(String[] args) {
System.out.println("Hello world!");
}
}
print("Hello world!")

12. "Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
12
print("Python" + " is " + "cool!")

13. 13
print("Python" + " is " + "cool!")
"Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
Big names using Python

14. "Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
14
print("Python" + " is " + "cool!")
Image Processing using Python
https://opencv.org/

15. "Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
15
print("Python" + " is " + "cool!")
Game Development using Python
https://www.pygame.org

16. "Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
16
print("Python" + " is " + "cool!")
Data Science using Python
https://matplotlib.org/

17. "Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
17
print("Python" + " is " + "cool!")
Natural Language Processing (NLP) and Text Mining using Python
https://github.com/amueller/word_cloud

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Let's now explore the Python universe!

19. How to install Python the Anaconda way
1. Download Anaconda (which includes Python):
https://www.anaconda.com/download/
2. Run the installer and follow the installation instructions
3. Run the Spyder editor and create your first Python program "helloworld.py"
19
Python Setup

20. • Variables store and give names to data values
• Data values can be of various types:
• int : -5, 0, 1000000
• float : -2.0, 3.14159
• bool : True, False
• str : "Hello world!", "K3WL"
• list : [1, 2, 3, 4], ["Hello", "world!"], [1, 2, "Hello"], [ ]
• And many more!
• In Python, variables do not have types!
• Data values are assigned to variables using "="
20
Variables and Data Types
x = 1 # this is a Python comment
x = x + 5
y = "Python" + " is " + "cool!"

21. 21
Variables and Data Types in Real Life

22. 22
Conditionals and Loops

23. • Cores of programming!
• Rely on boolean expressions which return either True or False
• 1 < 2 : True
• 1.5 >= 2.5 : False
• answer == "Computer Science" :
can be True or False depending on the value of variable answer
• Boolean expressions can be combined with: and, or, not
• 1 < 2 and 3 < 4 : True
• 1.5 >= 2.5 or 2 == 2 : True
• not 1.5 >= 2.5 : True
23
Conditionals and Loops

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Conditionals: Generic Form
if boolean-expression-1:
code-block-1
elif boolean-expression-2:
code-block-2
(as many elif's as you want)
else:
code-block-last

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Conditionals: Usia SIM (Driving license age)
age = 20
if age < 17:
print("Belum bisa punya SIM!")
else:
print("OK, sudah bisa punya SIM.")

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Conditionals: Usia SIM dengan Input
age = int(raw_input("Usia: ")) # use input() for Python 3
if age < 17:
print("Belum bisa punya SIM!")
else:
print("OK, sudah bisa punya SIM.")

27. 27
Conditionals: Grading
grade = int(raw_input("Numeric grade: "))
if grade >= 80:
print("A")
elif grade >= 65:
print("B")
elif grade >= 55:
print("C")
else:
print("E")

28. • Useful for repeating code!
• Two variants:
28
Loops
while boolean-expression:
code-block
for element in collection:
code-block

29. 29
While Loops
while raw_input("Which is the best subject? ") != "Computer Science":
print("Try again!")
print("Of course it is!")
while boolean-expression:
code-block

30. So far, we have seen (briefly) two kinds of collections:
string and list
For loops can be used to visit each collection's element:
30
For Loops
for element in collection:
code-block
for chr in "string":
print(chr)
for elem in [1,3,5]:
print(elem)

31. Conditionals and Loops in Real Life
31

32. • Functions encapsulate (= membungkus) code blocks
• Why functions? Modularization and reuse!
• You actually have seen examples of functions:
• print()
• raw_input()
• Generic form:
32
Functions
def function-name(parameters):
code-block
return value

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Functions: Celcius to Fahrenheit
def celsius_to_fahrenheit(celsius):
fahrenheit = celsius * 1.8 + 32.0
return fahrenheit
def function-name(parameters):
code-block
return value

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Functions: Default and Named Parameters
def hello(name_man="Bro", name_woman="Sis"):
print("Hello, " + name_man + " & " + name_woman + "!")
>>> hello()
Hello, Bro & Sis!
>>> hello(name_woman="Lady")
Hello, Bro & Lady!
>>> hello(name_woman="Mbakyu",name_man="Mas")
Hello, Mas & Mbakyu!

35. • Code made by other people shall be reused!
• Two ways of importing modules (= Python files):
• Generic form: import module_name
import math
print(math.sqrt(4))
• Generic form: from module_name import function_name
from math import sqrt
print(sqrt(4))
35
Imports

36. Functions in Real Life
36

37. • String is a sequence of characters, like "Python is cool"
• Each character has an index
• Accessing a character: string[index]
x = "Python is cool"
print(x[10])
• Accessing a substring via slicing: string[start:finish]
print(x[2:6])
37
String
P y t h o n i s c o o l
0 1 2 3 4 5 6 7 8 9 10 11 12 13

38. >>> x = "Python is cool"
>>> "cool" in x # membership
>>> len(x) # length of string x
>>> x + "?" # concatenation
>>> x.upper() # to upper case
>>> x.replace("c", "k") # replace characters in a string
38
String Operations
P y t h o n i s c o o l
0 1 2 3 4 5 6 7 8 9 10 11 12 13

39. >>> x = "Python is cool"
>>> x.split(" ") 39
String Operations: Split
P y t h o n i s c o o l
0 1 2 3 4 5 6 7 8 9 10 11 12 13
P y t h o n
0 1 2 3 4 5
i s
0 1
c o o l
0 1 2 3
x.split(" ")

40. >>> x = "Python is cool"
>>> y = x.split(" ")
>>> ",".join(y) 40
String Operations: Join
P y t h o n , i s , c o o l
0 1 2 3 4 5 6 7 8 9 10 11 12 13
P y t h o n
0 1 2 3 4 5
i s
0 1
c o o l
0 1 2 3
",".join(y)

41. Strings in Real Life
41

42. • Working with data heavily involves reading and writing!
• Data come in two types:
• Text: Human readable, encoded in ASCII/UTF-8, example: .txt, .csv
• Binary: Machine readable, application-specific encoding,
example: .mp3, .mp4, .jpg
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Input/Output

43. python
is
cool
43
Input
cool.txt
x = open("cool.txt", "r") # read mode
y = x.read() # read the whole
print(y)
x.close()

44. python
is
cool
44
Input
cool.txt
x = open("cool.txt", "r")
# read line by line
for line in x:
line = line.replace("n","")
print(line)
x.close()

45. python
is
cool
45
Input
cool.txt
x = open("C:UsersFarizcool.txt", "r") # absolute location
for line in x:
line = line.replace("n","")
print(line)
x.close()

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Output
# write mode
x = open("carpe-diem.txt", "w")
x.write("carpendiemn")
x.close()
# append mode
x = open("carpe-diem.txt", "a")
x.write("carpendiemn")
x.close()
Write mode overwrites files,
while append mode does not overwrite files but instead appends at the end of the files' content

47. Input in Real Life
47

48. Output in Real Life
48

49. • If a string is a sequence of characters, then
a list is a sequence of items!
• List is usually enclosed by square brackets [ ]
• As opposed to strings where the object is fixed (= immutable),
we are free to modify lists (that is, lists are mutable).
49
Lists
x = [1, 2, 3, 4]
x[0] = 4
x.append(5)
print(x) # [4, 2, 3, 4, 5]

50. 50
List Operations
>>> x = [ "Python", "is", "cool" ]
>>> x.sort() # sort elements in x
>>> x[0:2] # slicing
>>> len(x) # length of string x
>>> x + ["!"] # concatenation
>>> x[2] = "hot" # replace element at index 0 with "hot"
>>> x.remove("Python") # remove the first occurrence of "Python"
>>> x.pop(0) # remove the element at index 0

51. It is basically a cool way of generating a list
51
List Comprehension
[expression for-clause condition]
Example:
[i*2 for i in [0,1,2,3,4] if i%2 == 0]
[i.replace("o", "i") for i in ["Python", "is", "cool"] if len(i) >= 3]

52. • Like a list, but you cannot modify it (= immutable)
• Tuple is usually (but not necessarily) enclosed by parentheses ()
• Everything that works with lists, works with tuples,
except functions modifying the tuples' content
• Example:
52
Tuples
x = (0,1,2)
y = 0,1,2 # same as x
x[0] = 2 # this gives an error

53. List in Real Life
53

54. • As opposed to lists, in sets duplicates are removed and
there is no order of elements!
• Set is of the form { e1, e2, e3, ... }
• Operations include: intersection, union, difference.
• Example:
54
Sets
x = [0,1,2,0,0,1,2,2]
y = {0,1,2,0,0,1,2,2}
print(x)
print(y)
print(y & {1,2,3}) # intersection
print(y | {1,2,3}) # union
print(y - {1,2,3}) # difference

55. 55
Dictionaries
• Dictionaries map from keys to values!
• Content in dictionaries is not ordered.
• Dictionary is of the form { k1:v1, k2:v2, k3:v3, ... }
• Example:
x = {"indonesia":"jakarta", "germany":"berlin","italy":"rome"}
print(x["indonesia"]) # get value from key
x["japan"] = "tokyo" # add a new key-value pair to dictionary
print(x) # {'italy': 'rome', 'indonesia': 'jakarta', 'germany': 'berlin', 'japan': 'tokyo'}

56. Dictionary in Real Life
56

57. • While in functions we encapsulate a set of instructions,
in classes we encapsulate objects!
• A class is a blueprint for objects, specifying:
• Attributes for objects
• Methods for objects
• A class can use other classes as a base
• Generic:
57
Classes
class class-name(base):
attribute-code-block
method-code-block

58. class Person:
def __init__(self, first, last):
self.firstname = first
self.lastname = last
def describe(self):
return self.firstname + " " + self.lastname
guido = Person("Guido","Van Rossum")
print(guido.describe())
58
Classes: Person
class class-name(base):
attribute-code-block
method-code-block

59. 59
Classes: Person & Employee
class class-name(base):
attribute-code-block
method-code-block
# first add code for class Person here
class Employee(Person):
def __init__(self, first, last, staffnum):
Person.__init__(self, first, last)
self.staffnum = staffnum
def describe(self):
return self.lastname + ", " + str(self.staffnum)
guido = Employee("Guido", "Van Rossum", 123456)
print(guido.describe())

60. Class in Real Life
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61. 61
Lessons learned

62. 62
What's next?

63. 63
What's next? Keep learning!
https://stackoverflow.com/questions/tagged/python
https://docs.python.org
http://greenteapress.com/wp/think-python-2e/Python Official Documentation
Python on stackoverflow (QA website on programming)
Free Python e-book

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Food pack is ready,
enjoy your journey!