Python Programming Basics

Python is one of the powerful languages which has picked up the popularity after Machine Learning and Artificial Intelligence has boomed. I don't want to highlight on the why Python but how Python can be used.

Here are the list of contents

1. Installation
2. Libraries
3. Data Structures
4. Loops
5. Exercises

1. Installation

You get Python from Anaconda :)
Download Anaconda for your respective environments and install

Launch Anaconda Navigator and you will see few options like Jupyter notebook, spyder, orange, rstudio etc. launch Jupyter notebook for python.

Jupiter notebook will launch on your default browser and select the "New" -> "Python 3" option.
A new tab will be opened with option to play with python.

Click on the Untitled and rename appropriately as per your exercise/chapter.
That's it we are all set for to get our hands dirty.. Let's jump into programming.

2. Libraries

For the basic programming Python provides default libraries which need not be imported, but you would always want to take the advantage of inbuilt libraries for complex scenarios and faster execution then you need to import libraries.

Some of the libraries you would import are

numpy
pandas
matplotlib
scipy
sklearn

2.1 Numpy:

Numpy is package used for Scientific Computing like

a. Multi dimensional array
b. Methods for processing arrays
c. Linear algebra

2.2 Pandas:

Pandas are used for data analysis, we can analyze the data in Pandas with

a. Series - one dimensional array
b. DataFrames - two dimensional array consists of rows and columns.

Pandas are used to read the data from files (csv, tsv, excel, sql, json, url, dict)
Here is the cheatsheet for pandas for your reference.

2.3 Matplotlib:

Matplotlib is used for data representation in a visual form. The visualization of the data can be represented in the below formats

a. Bar Graphs
b. Pie Charts
c. Histogram
d. Scatter Plots and 3-D plotting

3. Data Structures

To hold the data we need some container or objects and also data could be of different type and formats, hence we have different data structures to hold these different types of data.

a. String, Int, Float
b. List
c. Tuple
d. Dictionary

String

String is a basic datatype which is used for storing the data.

Examples:
name = "Mr Python"
mobile = "3232001231"
address = "First Street, Frankfurt"

Operations: String operations can be found here.

Let's look at few of the operations:

1. Length: of the string:

Syntax: len(str) //where str is any string
Example:
name = "Mr Python"
length = len(name)
print(length)

2. Capitalize: Converts the first letter of the String to Upper case.

Syntax: str.capitalize() //where str is any string
Example:
name = "python"
# name.capitalize()
print( name.capitalize()) //returns 'Python'

Similarly we have upper() lower() and swapcase() for changing the alphabets to upper,lower and viceversa using these operations
title() - returns title case version of the string.

3. Count: returns the no. of occurrences of the substring.

Syntax: str.count(substr) //where str is any string and substr is any string
Example:
sentence = "python is a powerful language, is that true?"
count = sentence.count("is")
print(count) //returns 2

4. Find: returns the index of the substr if present in the str

Syntax: str.find(substr) //where str is any string and substr is any string
Example:
sentence = "python is a powerful language, is that true?"
count = sentence.find("powerful ")
print(count) //returns 12

4.  Index: returns the index of the substr if present in the str

Syntax: str.index(substr) //where str is any string and substr is any string
Example:
sentence = "python is a powerful language, is that true?"
count = sentence.index("powerful ")
print(count) //returns 12

5. Format: allows simple placeholders for formatting the statement

Syntax: format(str) //where str is any string
Example:
sentence = "Welcome {}, your room no is {}."
sentence = sentence.format("Hillton", 3033)
print(sentence ) //prints Welcome Hillton, your room no is 3033

6. isalnum: returns true if all the charecters of the string are alphanumeric

   Syntax: str.isalnum()//where str is any string
Example:
sentence = "Welcome123"
print(sentence.isalnum()) //prints true
sentence = "Welcome_123"
print(sentence.isalnum()) //prints false
sentence = " Welcome 123 "
print(sentence.isalnum()) //prints false

Similarly we have the following functions which are self explanatory
isalpha()
isdecimal()
isdigit()
isnumeric()

7. join: concatenates two strings

  Syntax: str.join(str2)//where str, str2 are any strings
Example:
sentence1 = 'Welcome123'
sentence2 = 'Welcome123'
print(sentence1.join(sentence2)) //prints Welcome123Welcome123

8. lstrip: left strip - removes the leading characters

Syntax: str.lstrip(str2)//where str, str2 are any strings
Example:
sentence1 = 'Welcome123'
sentence2 = 'Wel'
print(sentence1.lstrip(sentence2)) //prints true come123

9. rstrip: right strip - removes the trailing characters

Syntax: str.rstrip(str2)//where str, str2 are any strings
Example:
sentence1 = 'Welcome123'
sentence2 = '123'
print(sentence1.rstrip(sentence2)) //prints Welcome

10. strip: removes the leading & trailing characters

Syntax: str.strip(str2)//where str, str2 are any strings
Example:
sentence1 = '123Welcome123'
sentence2 = '123'
print(sentence1.strip(sentence2)) //prints Welcome

11. reversed: returns the List of reversed string with each characters as elements

Syntax: reversed(str)//where str, is any strings
Example:
sentence1 = 'Welcome123'
print(list(reversed(sentence1))) //prints ['3', '2', '1', 'e', 'm', 'o', 'c', 'l', 'e', 'W']

Lists

Tuples

Dictionaries

4. Loops

5. Exercises

1. Write a program to reverse a String.

Solution using loop:
givenString = input("Enter a String")
len1 = len(givenString)
rev = ""
while(len1 > 0):
rev += givenString[len1 -1]
len1 = len1 -1

print(rev)

Solution using slicing:

str1 = input("Enter a String")
rev = str1[:: -1]
print(rev)

Solution using Join & reversed functions:

str2 = input("Enter a String")
rev = ''.join(reversed(str2))
print(rev)

2. Write a program to find out if the given String is palindrome or not.

Solution:

str3 = input("Enter a String")

rev = str3[::-1]
if(rev == str3):
print("The given string is palindrome")
else:
print("The given string is not a palindrome")

3. Write a program to convert the list to list of squares

Given list1 = [1,2,3,4,5] Expected list2 = [1,4,9,16,25]

4. list prime numbers from 1 to 30

5. factorial of a given number.

6. Fibonacci series upto given number.

3. Write a program to convert each letter in the String to upper case if it is lower case and vice-versa:

Solution:

str3 = input("Enter a String")
caseStr = ""
for char in str3:
if(char.isupper()):
caseStr += char.lower()
else:
caseStr += char.upper()
print(caseStr)

4. Write a program to return the highest number which occurs in a series of number and how many times does it occur in the series.

ar = [23,46,23,56,]

\print(ar)

max_num = 0

for num in ar:

if(num>max_num):

max_num = num

print(max_num)

5. Write a program to print the below order for n =5

111

1111

11111

n = 5

for i in range(1, n+1):

print((10**i//(9)))

n = 5
for i in range(1, n+1):
    print((10**i//(9) * i))

1
121
12321
1234321

n = 5
for i in range(1, n):
    print((10**i//9) ** 2)


6. Write a program to Print 'Gent' or 'Lady' with the combination of substring words possible from a given string. Condition: Print 'Gent'  and no.of words that starts with CONSONENTS and 'Lady' and no.of words that starts with VOWELS.

str = 'ELEPHANT'
strLen= len(str)
Gent = 0
Lady = 0
vowels = 'AEIOU'


for i in range(strLen):

    if(str[0] not in vowels):
        Gent += strLen-i

    else:
        Lady += strLen-i

if(Gent > Lady ):
    print("Gent {}".format(Gent ))
elif(Kevin > Stuart):
    print("Lady {}".format(Lady ))
else:
    print("Nutral")


7. How to read a CSV file:

import pandas as pd

data = pd.read_csv("xyz.csv")
data.head(20)

//with encoding

data = pd.read_csv('xyz.txt',delimiter="\t", encoding = 'palmos')
data .head(20)

8. import pandas as pd
import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt

countries = pd.read_csv('D://$Kiran/personal/IIIT/companies.txt',sep = "\t",encoding = "ISO_8859_1")
countries
#countries.isnull().sum()
#countries.isnull().all(axis=1).sum()
//Displays the column's and the percentage of null values.
round(100*(countries.isnull().sum()/len(countries.index)), 2)

//Based on the above drop the columns which are having highest percentage of null values
countries = countries.drop('founded_at', axis=1)
countries = countries.drop('state_code', axis=1)
countries = countries.drop('region', axis=1)
countries = countries.drop('city', axis=1)
countries = countries.drop('homepage_url', axis=1)

round(100*(countries.isnull().sum()/len(countries.index)), 2)
countries[countries.isnull().sum(axis=1) > 1]



rounds2 = pd.read_csv('D://$Kiran/personal/IIIT/rounds2.csv', encoding = "ISO_8859_1")
round(100*(rounds2.isnull().sum()/len(rounds2.index)), 2)
rounds2 = rounds2.drop('funding_round_code', axis=1)
rounds2[np.isnan(rounds2['raised_amount_usd'])]

##apply the median value for the NaN values for the raised_amount_usd
rounds2.loc[np.isnan(rounds2['raised_amount_usd']), ['raised_amount_usd']] = rounds2['raised_amount_usd'].median()

# Filter the dataframe with 'private_equity'
gapminder_2007 = rounds2[rounds2['funding_round_type']=='private_equity']
gapminder_2007.shape

gapminder_2007.boxplot(by='company_permalink', column=['raised_amount_usd'], grid=False)
import matplotlib.pyplot as plt
plt.show()

df['gender'].value_counts()

 output:

 M=120
 F=80

With Normalize and Percentages
df['gender'].value_counts(Normalize=True)*100 #will convert output to percentages

  output:

  M=60
  F=40

7. Get the number from the list which appears odd no.of times.

def getOddEntry(lst):
 for i in lst:
  if lst.count(i) % 2 == 1:
   return i


8. Two List compare between same indexes.





return a_list[1] > b_list[0] and a_list[2]>b_list[1]


9. Input List with 





def equal(a, b, c):
    if len({a, b, c}) == 3:
        return 0
    return 4 - len({a, b, c})


output: 
equal(13, 4, 13) ➞ 2 
equal(11, 11, 11) ➞ 3 
equal(13, 14, 11) ➞ 0 






10. +ve no of integers/ Sum of -ve numbers 




def sum_neg(nums):
    if not nums: return []
    return [len([n for n in nums if n > 0]), sum(n for n in nums if n < 0)]


11. List to Unique List

return sorted(set(give_list))






12. Return the max no.of 
-> "000" or "00000" 

return max(s.split('1'))






13. rever + map + concatinate
-> input word 
-> output magic("banana") ➞ "0n0n0baca"
sol 1:

return word[::-1].translate(str.maketrans('aeou', '0123')) + 'aca'

sol 2:

v= {'a':'0','e':'1','o':'2','u':'3'}
  return ''.join(v[i] if i in v else i for i in word[::-1]) +'aca'



sol 3:

        word = word[::-1]

        str1 = ''
 for i in word:
  if(i == 'a'):
   str1 = str1 + str(0)
  elif(i == 'e'):
   str1 = str1 + str(1)
  elif(i == 'o'):
   str1 = str1 + str(2)
  elif(i == 'u'):
   str1 = str1 + str(3)
  else:
   str1 = str1 + str(i)
 
 str1 = str1 + 'aca'
 
 return str1






14. return first digit in a string 



for i in word[:]:
   if i.isdigit():
      return int(i)



15. Factorial
 

sol 1:

fact(n)

return n*fact(n-1) if n>1 else 1


sol 2:

def fact(n):
 count = 1
 for i in range(1, n+1):
  count = count * i
 
 return count












15. Upper or Lower Case with ASCII code reversed
sol 1:

input Xchar
return ord(Xchar.upper()) if Xchar.islower() else ord(Xchar.lower())

sol 2:

return ord(Xchar.swapcase())






16. Split string with multiple delimiters
import re
text = 'The quick brown\nfox jumps*over the lazy dog.'
print(re.split('; |, |\*|\n',text))


Output:

['The quick brown', 'fox jumps', 'over the lazy dog.']






17. Eval function - to check a given string condition

input: 

1. 2<3<-1>=9<0

2. -5<-2<0=0<3<6<200 




return eval(txt.replace('=', '==').replace('<==', '<=').replace('>==', '>='))





18. Eval function - to check a given string condition

Sample in out:

pie_chart({ "a": 1, "b": 2 }) ➞ 

     { "a": 120, "b": 240 }
pie_chart({ "a": 30, "b": 15, "c": 55 }) ➞ 

     { "a": 108, "b": 54, "c": 198 }
pie_chart({ "a": 8, "b": 21, "c": 12, "d": 5, "e": 4 }) ➞ 

    { "a": 57.6, "b": 151.2, "c": 86.4, "d": 36, "e": 28.8 }




Sol:
def draw_pie(data):
 result = dict()
 total = sum(data.values())
 for i in data:
            result.update({i: round(data[i]/total *360, 1)})
   
 return result
 





19. input string and add them with condition




sol:
def add_strings(num1, num2):

    # not ""
    if not num1:
        num1 = '0'
    if not num2:
        num2 = '0'
    try:
        return str(int(num1) + int(num2))
    except ValueError:
        return '-1'






20. return True or False if the first and second charecters are not in order of first<second index

sol 1:
def first_then_second(s1, xword, yword):
 return s1.rindex(xword) < s1.index(yword)





sol 2:
def first_then_second(s1, xword, yword):
  x = []
  y = s1.find(yword)
  for i in range(0, len(s1)):
    if s1[i] == xword:
      x.append(i)
    
  
  flag = True
  for i in x:
    if(i > y):
      flag = False
      return flag
  
  return flag







21. check the duplicate char's in each string of the phrase
Sol 1:

Output: True/False

def duplicate_chars_word_phrase(phrase):
return all(i.count(j)==1 for i in phrase.split() for j in i)

Sol 2:

def duplicate_chars_word_phrase(phrase):
  splt = phrase.split(" ")
  for word in splt:
    l = len(word)
    lst = []
    for i in word:
      lst.append(i)
    if(len(set(lst)) != l):
      return False
  
  return True






22. check the dots in 5 sided 

outout:



side = 1, => 1

side = 2, => 6

side = 3, => 16

side = 8, => 141




def 5Side(side):
 ans = 1
 for i in range(1,side):
    ans += (5*i)
 return ans







23. List of duplicates count which element has more no.of entries

input: ['J', 'K', 'L', 'L', 'J', 'L']

output: 'L'




Sol 1:

def max_entries(lst): 
  for i in set(lst):
    if lst.count(i)>len(lst)//2:
      return i
  return None



Sol 2:

def max_entries(lst):
 if len(lst) == 0:
  return None
 keys = dict()
 for i in lst:
  if keys.get(i) != None:
   keys.update({i:keys.get(i) + 1})
  else:
   keys.update({i: 1})
 max_value = max(keys.values());
 if max_value > len(lst)/2:
  return max(keys, key=keys.get)
 else:
  return None




24. Date conversion to a list format 
import dateutil.parser
def convert_date(date):
  date = dateutil.parser.parse(date)
  return [date.month, date.day, date.year]




25. Check is the list of lists with numbers form a circle.
input: [[2, 1], [1, 2]]

output: True

input: [[2, 1], [1, 0]]

output: False

def is_circular(lst):
  return sorted(i[0] for i in lst)==sorted(i[-1] for i in lst)









http://onlinestatbook.com/2/regression/intro.html

linear regression algorithm:

               Linear Regression comes under Supervise Machine Learning methods, where the past data with labels 

is used for building the model. A simple linear regression model explains the relationship between a dependent (output variable) and 

an independent (predictor variable) using a straight line which is also called as Best Fit Line.




The equation of best fit regression line is y = β₀ + β₁X + ϵ

interpret this as 'β₁' the average effort on 'y' for a one unit increase in 'X'.




β₀ is Y-intercept of the line 

β₁ is Slope of the line

ϵ is the residual error




Example:

Imagine Y as Distance traveled, X is the speed




AIM:  to find the best fit line using Least Square Method










 

  
  



  
  
X

  
  
ȳ

  
  
X-X̄

  
  
ȳ -ȳ

  
  
(X-X̄)2

  
  
(X-X̄) * (ȳ -ȳ)

 

  
  



  
  
1

  
  
3

  
  
-2

  
  
-0.6

  
  
4

  
  
1.2

 

  
  



  
  
2

  
  
4

  
  
-1

  
  
0.4

  
  
1

  
  
-0.4

 

  
  



  
  
3

  
  
3

  
  
0

  
  
-1.6

  
  
0

  
  
0

 

  
  



  
  
4

  
  
4

  
  
1

  
  
1

  
  
1

  
  
0.4

 

  
  



  
  
5

  
  
5

  
  
2

  
  
1.4

  
  
4

  
  
2.8

 

  
  
Mean

  
  
3

  
  
3.6

  
  



  
  



  
  
10

  
  
4

	X	ȳ	X-X̄	ȳ -ȳ	(X-X̄)2	(X-X̄) * (ȳ -ȳ)
	1	3	-2	-0.6	4	1.2
	2	4	-1	0.4	1	-0.4
	3	3	0	-1.6	0	0
	4	4	1	1	1	0.4
	5	5	2	1.4	4	2.8
Mean	3	3.6			10	4

Way to ML - Python - My Style