1. Betsy Manuel Trainer Foursteps Solutions
Python Programming
Betsy Manuel
Trainer
Foursteps Solutions
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2. Getting Started with PYTHON
What is PYTHON:
Invented by Guido van Rossum in the 1990s
Named after the comedy group Monty Python
Open source from the beginning
Managed by Python software foundation (PSF )
Aim – intelligence could be taught quickly and effectively.
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3. Powerful Standard library
Python Features:
Few Keywords, simple structure and
clear defined syntax
Easy to Learn
Let you get more done with less code and less time
Rapid Development
Strength of Python is the bulk of the library is portable and cross platform compactable
Powerful Standard library
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4. Who use Python today ?
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5. Python vs other popular language
Python C/C++ JAVA PHP Faster to learn Faster Faster Portable code Much smaller and compact code More powerful standard library More versatile Huge installed base
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6. Python vs other popular languages
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7. Python CLE and IDLE Editor
IDLE (Integrated DeveLopment Environment)
Completely written in Python and the Tkinter GUI toolkit
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8. Python Interpreter
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9. Awesome Standard Library
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10. Program Structure for Python
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11. Basic syntax Rules
Python is case sensitive. Hence a variable with name yoyostudytonight is not same as yoYoStudytonight
For path specification, python uses forward slashes. Hence if you are working with a file, the default path for the file in case of Windows OS will have backward slashes, which you will have to convert to forward slashes to make them work in your python script.
For window's path C:\folderA\folderB relative python program path should be C:/folderA/folderB
3. In python, there is no command terminator, which means no semicolon ; or anything.
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12. In one line only a single executable statement should be written and the line change act as command terminator in python.
To write two separate executable statements in a single line, you should use a semicolon ;to separate the commands. For example,
In python, you can write comments in your program using a # at the start. A comment is ignored while the python script is executed.
Line Continuation: To write a code in multiline without confusing the python interpreter, is by using a backslash \ at the end of each line to explicitly denote line continuation. For example,
sum = \
456 + \
789
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13. Blank lines in between a program are ignored by python.
This is the most important rule of python programming. In programming language like Java, C or C++, generally curly brackets { } are used to define a code block, but python doesn't use brackets, then how does python knows
It is recommended to use tab for indentation
if True:
print "Yes, I am in if block"
# the above statement will not be
# considered inside the if block
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14. Program with main and function definition
Reused code
Function Definition
Main program
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15. Blocks and Indentation
>>> Def add(a):
b=0
b = a+b
return b
>>> Add(a)
>>> Def add(a):
b=0
b = a+b
return b
Add(a)
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16. Print Statements
Before we do anything, we need a way to look at values using the print command.
print < expression >
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17. Comments
A comment is used to enter freehand text, usually for documentary purposes
Use a single hashmark to comment #
Comment ends with new line
# this is a comment
def sum(): # this is the sum function
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18. Variables, Operators and Expression
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19. Variable as String
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20. Variable as number
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21. Operators of python
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22. Python for Comparison Operators
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23. Python Arithmetic operators
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24. Python for Logical Operators
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25. Python for Assignment Operators
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26. Built in Automatic Data types
Numbers, lists, strings, tuples, tuples, dictionaries, etc.
Numbers:
Integers
5, -8, 43, -234, 99933
Floats
6.8, 24e12, -4e-2 #2e3 = 2000, scientific notation
Complex numbers:
4+3j, j
Booleans
True, False
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27. Precedence Built in functions
>>> round (7.78)
>>> int (230.5)
>>> float (230)
>>> int (3e3)
>>> type (151.0)
>>> type (151)
>>> type ('Python')
>>> 5-2*3/4 >>> 50/2+2**3-8/2
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28. Precedence Built in functions
>>> round (7.78)
# Built-in function returns: 8
>>> int (230.5)
# Built-in converts to integer, returns: 230
>>> float (230)
# Built-in converts to float, returns: 230.0
>>> int (3e3) # returns: 3000
>>> type (151.0) # returns: <type 'float'>
>>> type (151) # returns: <type 'int'>
>>> type ('Python') # returns: <type 'str'>
>>> 5-2*3/4 4 # same as 5-((2*3)/4)
>>> 50/2+2**3-8/ # (50/2)+(2**3)-(8/2)
# For equal precedence go from left to right!
# first power, then left division, then add them,
# then right division, then subtraction
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29. Calling Python’s Library functions in module
>>> import math # imports the math module
# now we can use math’s functions
>>> math.pi # call a math library constant
>>> math.ceil (3.14) 4 # call a module function ()
>>> math.sqrt (64) # call square-root function
>>> import random # import the random module
>>> x = random.uniform (1, 5) # returns a float between 1 and 5
>>> x
>>> x = random.randint (1, 5) # returns an integer between 1 and 5
>>> x 1
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30. Built in numeric function – Examples
>>> range (6, 18, 3)
>>> range (10)
>>> abs (-17)
>>> max (12, 89)
>>> round (12.7)
>>> hex (10)
>>> oct (10)
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31. Built in numeric function – Examples
>>> range (6, 18, 3) # returns: [6, 9, 12, 15]
>>> range (10) # returns: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> abs (-17) # returns: 17
>>> max (12, 89) # returns: 89
>>> round (12.7) # returns: 13.0
>>> hex (10) # returns: '0xa‘
>>> oct (10) # returns: '012'
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32. Use built in function
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33. Conditional statements, Loop and Iterations
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34. Conditions in PYTHON
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35. If … else statements for python
the program evaluates the test expression and will execute
statement(s) only if the text expression is True.
Syntax :
If test expression :
Statement(s)
Examples:
>>>a=6
>>> if a>0:
print (a “is positive number”)
>>> a=-1
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36. Python if...else Statement
Syntax:
if test expression:
Body of if
else:
Body of else
Example :
>>> a=9
>>> if a>5:
print (a “is greater than 5”)
else :
print (a, ”is less than 5”)
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37. Python if...elif...else statements
Syntax :
if test expression:
Body of if
elif test expression:
Body of elif
else:
Body of else
Try by yourself
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38. FOR LOOP for PYTHON
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39. Print out the weeks names in our for loop
LOOPs for Python
For - Loop
Executes a sequence of statements multiple times and abbreviates the code that manages the loop variable.
Print out the weeks names in our for loop
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40. (cont’d) For loop in range limit >>> for a in range(3, 10)
print a
For loop with BREAK point
>>> for i in range(3, 10):
if(i==7): break
print i
For loop for continue statement
>>> for x in range(10, 20):
if (x%5 ==0): continue
print x
For loop with enumeration
>>> months= ["jan", "feb", "mar", "april", "May", "june"]
>>> for i, m in enumerate(months):
print I, m
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41. (cont’d) For loop in range limit >>> for a in range(3, 10)
print a result : 3, 4,5 , 6, 7, 8, 9, 10
For loop with BREAK point
>>> for i in range(3, 10):
if(i==7): break
print i result: 3, 4, 5, 6
For loop for continue statement
>>> for x in range(10, 20):
if (x%5 ==0): continue
print x result : 11, 12, 13, 14,16, 17, 18, 19
For loop with enumeration
>>> months= ["jan", "feb", "mar", "april", "May", "june"]
>>> for i, m in enumerate(months):
print I, m
0 jan
Feb
Mar
April
May
June
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42. While LOOP for PYTHON Syntax of while Loop in Python
While test_expression:
Body of while
Example :
>>> n=10
>>> s=0
>>> i=1
>>> while i<=n:
s=s+i
i=i+1
>>> print s
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43. While LOOP for PYTHON Syntax of while Loop in Python
While test_expression:
Body of while
Example :
>>> n=10
>>> s=0
>>> i=1
>>> while i<=n:
s=s+i
i=i+1
>>> print s Print : 55
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44. while loop with else Same as that of for loop
The else part is executed if the condition in the while loop evaluates to False.
Examples:
>>> a=0
>>> while a<3:
print "inside"
a=a+1
>>> else:
print “outside”
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45. Python for conditional operators
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46. EXERCISE Greatest of three numbers
to check whether an integer is a prime number or not using for loop and if...else statement
to check whether a number entered by the user is even or odd.
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47. Dictionary & List
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48. Lists – Lets play with LIST
List is an ordered collection of objects
List is modifiable
They can have elements of different types
Elements are comma separated in list
>>> names = [mala, lala, kala ] # assigns to the rivers list
>>> x = ['apple', 3, [4.0, 5.0]] # multi-type list
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49. List indices X = [ ‘josh ‘sibi’ Athi Mohan barathi ] + index 1 2 3 4
Lists start counting from 0 on the left side (using + numbers) and -1 from the right side
>>> x = [‘josh', ‘sibi', ‘Athi', ‘mohan', ‘barathi']
>>> X[2]
>>> X[-5]
>>> x[:3]
>>> X[0:3]
>>> x[3:10]
>>> x[3:]
X = [
‘josh
‘sibi’
Athi
Mohan
barathi ]
+ index 1 2 3 4
- Index -5 -4 -3 -2 -1
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50. List indices X = [ ‘josh ‘sibi’ Athi Mohan barathi ] + index 1 2 3 4
Lists start counting from 0 on the left side (using + numbers) and -1 from the right side
>>> x = [‘josh', ‘sibi', ‘Athi', ‘mohan', ‘barathi']
>>> X[2] ‘Athi’
>>> X[-5] ‘josh’
>>> x[:3] [ josh', ‘sibi', ‘athi']
>>> X[0:3] [ josh', ‘sibi', ‘athi'] # includes 0 but excludes 3
>>> x[3:10] [‘mohan', ‘barathi'] # ignores if the items don’t exist
>>> x[3:] [‘mohan', ‘barathi'] # index 3 and higher
X = [
‘josh
‘sibi’
Athi
Mohan
barathi ]
+ index 1 2 3 4
- Index -5 -4 -3 -2 -1
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51. (cont’d)
>>> lang = ['P', ‘Y', 'T', 'H', 'O', 'N'] >>> lang[3] 'H‘ >>> lang[-1] 'N‘ >>> lang[-6] 'P‘ >>> lang[-8] Traceback (most recent call last): File "<interactive input>", line 1, in <module>IndexError: list index out of range >>> lang[:3] ['P', ‘Y', 'T'] >>> lang [-3:] ['H', 'O', 'N'] P Y T H O N 1 2 3 4 5 6 -6 -5 -4 -3 -2 -1
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52. (cont’d)
>>> x [:-2] -> [‘hydroxide’, ‘phosphate’, ‘carbonate’]
# up to, but not including index -2, i.e., gets rid of the last two
>>> x [2:] -> [‘carbonate’, ‘oxide’, ‘silicate’] # values from position 2 to the end (inclusive)
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53. List with mixed data types
The len () functions returns the number of elements in a list
>>> x = [1, 2, 3, [3, 4]] ; len (x)
Returns 4
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54. List Built- in functions
Insert
Remove
Pop
Del
Sort
Append
Extend
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55. List can change >>> x = ['River', 'Lake', 'Rock']
>>> x[1] = 'Horse‘
>>> x[0:]
['River', 'Horse', 'Rock']
>>> y = x[:] # copies all x’s elements and assigns to y
>>> y[0] = 'Timber‘ # substitute
>>> y[2] = 'Lumber‘ # substitute
>>> y[0:] #show y from the beginning
['Timber', 'Horse', 'Lumber']
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56. List can change
>>> x = ['River', 'Lake', 'Rock'] >>> x[1] = 'Horse‘ >>> x[0:] ['River', 'Horse', 'Rock'] >>> y = x[:] # copies all x’s elements and assigns to y >>> y[0] = 'Timber‘ # substitute >>> y[2] = 'Lumber‘ # substitute >>> y[0:] #show y from the beginning
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57. Modify List >>> x=[1,2,3,4] >>> y=[5,6]
>>> x.append(y) # adds y as an element (in this case a list) to the end of x
>>> print x [1, 2, 3, 4, [5, 6]]
>>> y = [5,6]
>>> x.extend(y) # adds the items to the end of an existing list
>>> print x [1, 2, 3, 4, 5, 6]
>>> x.insert(2, 'Hello') # inserts an element after a given index; always needs two arguments
>>> print x [1, 2, 'Hello', 3, 4, 5, 6]
>>> x.insert(0, 'new') # insert at the beginning (at index 0) an new item
>>> print x ['new', 1, 2, 'Hello', 3, 4, 5, 6]
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58. Sorting lists
>>> x = [ 'Mercury', 'Venus', 'Earth', 'Mars', 'Jupiter', 'Saturn', 'Uranus', 'Neptune']
>>> x.sort()
>>> print x
['Earth', 'Jupiter', 'Mars', 'Mercury', 'Neptune', 'Saturn', 'Uranus', 'Venus']
>>> x=[2, 0, 1,'Soon', “man"]
[0, 1, 2, 'Man', 'Soon']
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59. Min, Max, index and count functions
#returns the index for ‘-3’
>>> x.index(65) 4
#returns the index for ‘45’
>>> x = [6, 9, 4, 7, 9, 2, 9]
>>> x.count(9) 3
>>> x = [‘car’, van, bike, scotty]
>>> min (x) ‘bike‘
>>> max (x) ‘van‘
>>> x = [6, 1, -5, 15, 78]
>>> min (x) -5
>>> max (x) 78
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60. Dictionaries – {}
Called dictionary because they allow mapping from arbitrary objects
Values in a dictionary are accessed via keys that are not just numbers
Both lists and dictionaries store elements of different types
Values in a list are implicitly ordered by their indices
Those in dictionaries are unordered
>>> x = {} # create an empty dictionary
>>> x[0] = 'Mercury‘ # assigns a value to a dictionary variable as if it is a list
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61. (cont’d) >>> x = {} # declare x as a dictionary
>>> x[“aa"] = 2 # indexing with non numbers (in this case string)
>>> y = {}
>>> y[bb'] = 5
>>> x[‘aa'] * y [‘bb'] # this cannot be done with lists (need int indices) 10
>>> phone = {} # declare phone as a dictionary
# dictionaries are great for indexing lists by names (lists cannot do it)
>>> phone [‘baby'] =
>>> print phone[‘baby']
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62. (cont’d) >>> emp= {} # new dictionary
>>> emp[“name"] = “Mohan“ # uses list format
>>> emp[" 'COM "] = “HCL“
>>> emp["RES"] = “Tambaram“
>>> print emp {‘name': Mohan', 'RES': tambaram', 'COM': HCL'}
>>> del emp[“name"]
>>> print emp {'IND': ‘HCL', 'RES': Tambaram'}
>>> emp.keys() ['IND', 'RES']
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63. Tuples
Tuples are as same as List, but tuples are immutable and cannot be changed
Difference between tuple and list are , the tuples cannot be changed unlike lists and tuples use parentheses, whereas lists use square brackets.
It is declared with the syntax
X = (x1,x2)
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64. Operations that can be done with tuple
Addition : possible to add more data to a tuple. This can be done using the addition operator.
t = (1, 2, 3, 4, 5)
t = t + (7,)
print t
Deletion: to delete a tuple, the del keyword is used
del t
Slicing: Slicing in tuples, works exactly the same like in the case of lists
>>> t = (1, 2, 3, 4)
>>> t[2:4]
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65. In keyword: It is used to check, if any element is present in the sequence or not. It returns True if the element is found, otherwise False. For example,
>>> t = (1, 2, 3, 6, 7, 8)
>>> 2 in t
>>> 5 in t
True
False
Len()
cmp()
max() and min()
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66. Functions and Functions Arguments
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67. Function definitions User defined function object
func_def : "def" func_name "(" [parameter_list] ")" ":“
parameter_list: (def parameter ",")
Syntax for function :
def function name():
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68. Self describe function
Exercise :
Self describe function
Simple Function format:
>>> def simple():
print “Function is done"
>>> simple() Return : Function is done
Functions with arguments :
>>> def mul (a, d):
print (a*d)
>>> add(2, 4) Return : 8
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69. Multiple Function Parameters
>>> def add(x, y): sum = x+y print sum >>> def main(): add(2, 3) add(22.3, 55.6) a=int(input("enter the integer1")) b=int(input("enter the integer2")) add(a, b) >>> main() enter the integer1: 12 enter the integer2: 2 14
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70. Return the function values
Return the value for the main function
def sum(a):
return a+5
print sum(3) print : 8
print (sum(4)+sum(5)) print : 19
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71. Global vs. Local variables
Variable defined inside the function is LOCAL SCOPE and those defined outside the function is GLOBAL SCOPE
>> sum= 0 # global variable
>> def f(x1, x2): # function declaration
sum = x1+x2
Print sum
return sum
>> f(100, 200) print : 300 (local variable)
>> print (sum) print : 0 (global variable)
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72. The Anonymous Functions
Anonymous is not declared in the standard manner by using the def keyword
Lambda forms can take any number of arguments but return just one value in the form of an expression. 
Cannot access other variable other than those in parameters list
Syntax :
lambda [arg1, arg2,,,,argn ]: expression
Example:
>>Sum = lambda a1, a2: a1+a2
>>Sum(10, 20) print : 30
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73. Write a Programs with function module
Factorial program using function module
# Python program to find the factorial of a number provided by the user.# change the value for a different result
num = 4
factorial = 1
for i in range(1,num + 1):
factorial = factorial*I
print("The factorial of", num ,"is", factorial)
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74. Thank you
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