A dummies guide to python
I understand. You’re tired. You just want to start programming in Python so you can start doing cool projects.
Well the good thing is that Python is a very intuitive language. Its actually the preferred language for data scientists (sorry R!). So I have assembled a quick guide for you to learn Python in a matter of minutes!
Python falls in the class of object-oriented languages. It has many great libraries for data science including pandas, numpy, sci-kit learn, matplotlib etc.
This aim of this guide is for you to get up to speed with Python so you hit the ground running.
We will be using Python 3 (the latest iteration)
For this lesson we wont be installing and IDE on our computer. We will use an online IDE to compile our code. For that please click HERE
First Program
#Open the IDE
#The first program for any programming language is “Hello World”
print ("Hello World")
# Execute
Hello World
Base Types
# Integer
# int 5 56 69 0
int = 5 56 69 0
# Float
# float 9.45 0.55
float = 9.45 0.55
# Boolean
# bool True False
# String
# str "One" "Ahsan"
str = "One" , "Ahsan"
Variables in Python
# Declaring a variable
# Whenever you use = you are assigning a value to some variable
#For example we use an integer
a = 1
print (a)
# Execute
1
# Re-assigning string to the same variable
a = "Ahsan"
print (a)
# Execute
Ahsan
#Concatenate Variables a & b
a = "Ahsan"
b = 1989
print (a+b)
# Execute
Traceback (most recent call last):
File "python", line 4, in <module>
TypeError: must be str, not int
# We got an error becasue we cannot add an integer & a string
# Hence we will convert integer to a string
# Use str function
print (a+str(b))
# Execute
Ahsan1989
# If we want to add a space between an integer and string
# Use " "
print (a+" "+str(b))
# Execute
Ahsan 1989
#Deleting a variable
# Delete b
del b
print (a+" "+str(b))
# Execute
Traceback (most recent call last):
File "python", line 8, in <module>
NameError: name 'b' is not defined
# b gets deleted hence the above NameError
Transforming Variables
#Accessing value in strings
a = "Ahsan"
print(a[0])
# Execute
A
# 0 is the first position in the variable
# Same can be done with multiple variables
a = "Ahsan"
b = "Will be teaching you python"
c = "How cool is that?"
print(a[0:5],b[0:20],c[0:8])
# Execute
Ahsan Will be teaching you How cool
Lists
# A list is a container type for storing different base types in Python
# also called an array
# List can be changed
list1 = [1, 2, 4]
list2 = ["Ahsan", "Anis", 1989]
# Accessing different values in a list
print(list1[1])
# Execute
2
print(list2[0:1])
# Execute
['Ahsan']
Tuples
# Tuples are like lists but are immutable meaning they cannot be changed
tuple1 = (1, 2, 4)
tuple2 = ("Ahsan", "Anis", 1989)
print(tuple2[0:1])
# Execute
('Ahsan',)
Dictionary
# Dictionary is an immutable data type such as strings, numbers, or tuples
dict = {'Name': 'Ahsan', 'Age': 28, 'Position': 'Data Scientist'}
print (dict['Name'], dict['Age'], dict['Position'])
# Execute
Ahsan 28 Data Scientist
# Can also be written like this
dict = {'Name': 'Ahsan', 'Age': 28, 'Position': 'Data Scientist'}
print ("dict['Name']: ", dict['Name'])
print ("dict['Age']: ", dict['Age'])
print("dict['Position']:", dict['Position'])
# Execute
dict['Name']: Ahsan
dict['Age']: 28
dict['Position']: Data Scientist
Arrays
# An array is a 1 dimensional data structure also known as a scalar
arr = [100, 200, 300, 400, 500]
print (arr[1:4])
# Execute
[200, 300, 400]
Matrix
# A A matrix is a 2 dimensional data structure
matrix = [['Ahsan',8,8,8,8,8],
['Anis',9,9,9,9,9],
['Data',0,0,0,0,0],
['Scientist',1,1,1,1,1]]
print (matrix)
# Execute
[['Ahsan', 8, 8, 8, 8, 8], ['Anis', 9, 9, 9, 9, 9], ['Data', 0, 0, 0, 0, 0], ['Scientist', 1, 1, 1, 1, 1]]
Arithmetic Operators
# Addition
a = 100
b = 10
print (a+b)
# Execute
110
# Subtraction a-b = 90
# Multiplication a * b = 1000
# Division a / b = 10
# Modulus a % b = 0 , b % a = 10
# Exponent a**b = 100000000000000000000
If statement
# If statetemnt is a boolean expression followed by one or more statements
# Boolean statement are either True or False
a = 100
if a > = 10:
print ("Thats a big number")
# Execute
Thats a big number
If…Else statement
#If statement runs like usual, Else statement run if the first statement is False
a = 9
if a >= 10:
print ("Thats a big number")
else:
print ("Not a big number")
# Execute
Not a big number
Elif statement
# Elif statement is a statement which you put after if statement
a = 1
if a > 0:
print ("Thats a big number")
elif a == 0:
print ("Not a big number")
else:
print ("Put another number")
# Execute
Thats a big number
a = 0
if a > 0:
print ("Thats a big number")
elif a == 0:
print ("Not a big number")
else:
print ("Put another number")
# Execute
Not a big number
a = -2
if a > 0:
print ("Thats a big number")
elif a == 0:
print ("Not a big number")
else:
print ("Put another number")
# Execute
Put another number
Nested if statements
# An if, else, elif statement within an if, else, elif statement is called a nested if statement
num = float(input("Enter a number: "))
if num >= 0:
if num == 0:
print("Zero")
else:
print("Positive number")
else:
print("Negative number")
For Loop
# a for loop executes till the last statement is reached
numbers = [1, 2, 2, 8, 4]
sum = 0
for val in numbers:
sum = sum+val
print("The sum is", sum)
# Execute
('The sum is', 17)
For loop with else
# Exactly like for loop, just that the else statement is printed at the end
numbers = [1, 2, 3, 4, 5 , 6, 7, 8, 9, 10]
for i in numbers:
print(i)
else:
print("All numbers printed.")
# Execute
1
2
3
4
5
6
7
8
9
10
All numbers printed.
While loop
# a while loop iterates the statement as long as the statement is True
number = 0
while (number <= 10):
print 'The count is:', number
number = number + 1
print "All numbers printed"
# Execute
The count is: 0
The count is: 1
The count is: 2
The count is: 3
The count is: 4
The count is: 5
The count is: 6
The count is: 7
The count is: 8
The count is: 9
The count is: 10
All numbers printed
While loop with else
# Same as while loop, else statement is executed when logic is false
counter = 0
while counter <= 10:
print("loop")
counter = counter + 1
else:
print("end loop")
# Execute
loop
loop
loop
loop
loop
loop
loop
loop
loop
loop
loop
end loop
Break statement
# Break statement is used to stop the loop in its tracks
for val in "Ahsan":
if val == "n":
break
print(val)
print("loop end")
# Execute
A
h
s
a
loop end
Continue statement
# Continue statement unlike break continues to print the statement till it finishes
for val in "Ahsan":
if val == "a":
continue
print(val)
print("loop end")
# Execute
A
h
s
n
loop end
Good Python