Python

Variable Naming Technique:
    
Camel Case:
variableNameOne = 'John'

Pascal Case
VariableNameOne = 'john'

MyVariableName = 'John'
variable_name_one = 'John'

Variables:
    
Declare Variable:
VariableName1 = 'VariableValue'
VariableName2 = VariableName1
VariableName3 = VariableName1 + VariableName2
VariableName4, VariableName5, VariableName6 = '1', '2', '3'
VariableName7 = '''I am a teacher and enjoy teaching.


Data Type:
VariableName = 5
VariableName = str('Hello World')	str	
VariableName = int(20)	int	
VariableName = float(20.5)	float	
VariableName = complex(1j)	complex	
VariableName= list(('apple', 'banana', 'cherry'))	list	
VariableName= tuple(('apple', 'banana', 'cherry'))	tuple	
VariableName= range(6)	range	
VariableName= dict(name='John', age=36)	dict	
VariableName= set(('apple', 'banana', 'cherry'))	set	
VariableName= frozenset(('apple', 'banana', 'cherry'))	frozenset	
VariableName= bool(5)	bool	
VariableName= bytes(5)	bytes	
VariableName= bytearray(5)	bytearray	
VariableName= memoryview(bytes(5))	memoryview

View Data Type:
print(type(VariableName))

Calculations:
print('Addition', 2 + 3)   # addition(+)
print('Subtraction', 3 - 1)   # subtraction(-)
print('Multiplication', 2 * 3)   # multiplication(*)
print('Division', 3 / 2)   # division(/)
print('exponential', 3 ** 2)  # exponential(**)
print('modulus', 3 % 2)   # modulus(%)
print('Division without remiander', 3 // 2)  # division without remainder

Replace numbers with variable names to calculate variables.

Operators:
print(3 > 2)     # True, because 3 is greater than 2
print(3 >= 2)    # True, because 3 is greater than 2
print(3 < 2)     # False,  because 3 is greater than 2
print(2 < 3)     # True, because 2 is less than 3
print(2 <= 3)    # True, because 2 is less than 3
print(3 == 2)    # False, because 3 is not equal to 2
print(3 != 2)    # True, because 3 is not equal to 2
print(len(first_name)) # Number of characters
print(len('mango') == len('avocado'))  # False
print(len('mango') != len('avocado'))  # True
print(len('mango') < len('avocado'))   # True
print(len('milk') != len('meat'))      # False
print(len('milk') == len('meat'))      # True
print(len('tomato') == len('potato'))  # True
print(len('python') > len('dragon'))   # False

Boolean:
print('True == True: ', True == True)
print('True == False: ', True == False)
print('False == False:', False == False)
print('True and True: ', True and True)
print('True or False:', True or False)

AND, OR and NOT:
print(3 > 2 and 4 > 3) # True - because both statements are true
print(3 > 2 and 4 < 3) # False - because the second statement is false
print(3 < 2 and 4 < 3) # False - because both statements are false
print(3 > 2 or 4 > 3)  # True - because both statements are true
print(3 > 2 or 4 < 3)  # True - because one of the statement is true
print(3 < 2 or 4 < 3)  # False - because both statements are false
print(not 3 > 2)     # False - because 3 > 2 is true, then not True gives False
print(not True)      # False - Negation, the not operator turns true to false
print(not False)     # True
print(not not True)  # True
print(not not False) # False

Strings Manipulators:
\n # Line break
print('This is an \nexample of a lione break')
\t # Tab content
print('Days\tTopics\tExercises'

print(VariableName.capitalize()) # Captitilize first character#
print(VariableName.count('y')) # Count occurances of y
print(VariableName.count('th')) # Count occurances of th
print(VariableName.endswith('on'))   # Does value end with 'on'
print(VariableName.endswith('tion')) # Does value end with 'tion'

VariableName = 'I am {} {}. I am a {}. I live in {}.'.format(VariableName, VariableName2, VariableName3, VariableName4)
print(VariableName)

VariableName = 10
VariableName2 = 3.14
VariableName3 = VariableName2
output = 'The area of circle with {} is {}'.format(str(VariableName), str(VariableName3))
print(output)

language = 'Python'
first_letter = language[0]
print(first_letter) # P

second_letter = language[1]
print(second_letter) # y

last_index = len(language) - 1
last_letter = language[last_index]
print(last_letter) # n

first_three = language[0:3] # starts at zero index and up to 3 but not include 3
print(first_three) # pyt
last_three = language[3:6]
print(last_three) # hon
middle_three = language[2:4]
print(last_three) # tho

Lists:
    
Declare Lists:
    
fruits = ['banana', 'orange', 'mango', 'lemon']                     # list of fruits

# Show list
print('Fruits:', fruits)

# Show number of values in list
print('Number of fruits:', len(fruits))

# First index
first_fruit = fruits[0] # we are accessing the first item using its index
print(first_fruit)      # banana

# Second index
second_fruit = fruits[1]
print(second_fruit)     # orange

# Last index
last_fruit = fruits[3]
print(last_fruit) # lemon

# Second Last index
last_fruit = fruits[-1]
print(last_fruit) # lemon

# List All list items
all_fruits = fruits[0:4] # it returns all the fruits
orange_and_mango = fruits[1:3] # it does not include the end index

# Change list value
fruits = ['banana', 'orange', 'mango', 'lemon'] 
fruits[0] = 'Avocado' 
print(fruits)       #  ['avocado', 'orange', 'mango', 'lemon']
fruits[1] = 'apple'
print(fruits)       #  ['avocado', 'apple', 'mango', 'lemon']
last_index = len(fruits) - 1
fruits[last_index] = 'lime'
print(fruits)        #  ['avocado', 'apple', 'mango', 'lime']

# checking items
fruits = ['banana', 'orange', 'mango', 'lemon']
does_exist = 'banana' in fruits
print(does_exist)  # True
does_exist = 'lime' in fruits
print(does_exist)  # False

# Append
fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.append('apple')
print(fruits)           # ['banana', 'orange', 'mango', 'lemon', 'apple']
fruits.append('lime')   # ['banana', 'orange', 'mango', 'lemon', 'apple', 'lime]
print(fruits)

# insert
fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.insert(2, 'apple') # insert apple between orange and mango
print(fruits)           # ['banana', 'orange', 'apple', 'mango', 'lemon']
fruits.insert(3, 'lime')   # ['banana', 'orange', 'apple', 'mango', 'lime','lemon',]
print(fruits)

# remove
fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.remove('banana')
print(fruits)  # ['orange', 'mango', 'lemon']
fruits.remove('lemon')
print(fruits)  # ['orange', 'mango']

# del 
fruits = ['banana', 'orange', 'mango', 'lemon']
del fruits[0]     
print(fruits)       # ['orange', 'mango', 'lemon']

del fruits[1]     
print(fruits)       # ['orange', 'lemon']
del fruits
print(fruits)       # This should give: NameError: name 'fruits' is not defined

# Copy list
fruits = ['banana', 'orange', 'mango', 'lemon']
fruits_copy = fruits.copy()     
print(fruits_copy)       # ['banana', 'orange', 'mango', 'lemon']

# join
positive_numbers = [1, 2, 3,4,5]
zero = [0]
negative_numbers = [-5,-4,-3,-2,-1]

integers = negative_numbers + zero + positive_numbers
print(integers)

fruits = ['banana', 'orange', 'mango', 'lemon']
vegetables = ['Tomato', 'Potato', 'Cabbage','Onion', 'Carrot'] 
fruits_and_vegetables = fruits + vegetables
print(fruits_and_vegetables )

# count
fruits = ['banana', 'orange', 'mango', 'lemon']
print(fruits.count('orange'))   # 1
ages = [22, 19, 24, 25, 26, 24, 25, 24]
print(ages.count(24))           # 3

# sort
fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.sort()
print(fruits) 

fruits.sort(reverse=True)
print(fruits)