Python_Cheat_Sheet.txt

#Print-Prints a string into the console. 
print("Hello World")

#Input-Prints a string into the console, and asks the user for a string input.
input("What's your name")

#Comments-Adding a # symbol in font of text.The computer will ignore your comments.
#This is a comment
print("This is code")

#Variables-A variable give a name to a piece of data.Like a box with a label, it tells you what'sinside the box.
my_name = "Angela"
my_age = 12

#The += Operator-This is a convient way of saying: "take the previous value and add to it.
my_age = 12
my_age += 4
#my_age is now 16

#Integers-Integers are whole numbers. 
my_number = 354

#Floating Point Numbers-Floats are numbers with decimal places.
my_float = 3.14159

#Strings-A string is just a string of characters.It should be surrounded by double quotes.
my_string = "Hello"

#String Concatenation-You can add strings to string to create a new string. This is called concatenation.
"Hello" + "Angela"
#becomes "HelloAngela"

#Escaping a String-Because the double quote is special, it denotes a string, if you want to use it in a string, you need to escape it with a "\"
speech = "She said: \"Hi\""
print(speech)
#prints: She said: "Hi"

#Converting Data Types-You can convert a variable from 1 data type to another.
=Converting to float:
float()
=Converting to int:
int()
=Converting to string:
str()
n = 354
new_n = float(n)
print(new_n) #result 354.0

#Checking Data Types-You can use the type() function to check what is the data type of a particular variable.
n = 3.14159
type(n) #result float

#F-Strings-You can insert a variable into a string using f-strings.
days = 365
print(f"There are {days} in a year")

#The += Operator-This is a convenient way to modify a variable. It takes the existing value in a variable and adds to it.
my_number = 4
my_number += 2
#result is 6

#The Modulo Operator-The modulo does not give you the result of the division, just the remainder.
e.g. 4 ÷ 2 = 2 with no remainder
but 5 ÷ 2 = 2 with 1 remainder
5 % 2
#result is 1

#Arithmetic Operators
3+2 #Add
4-1 #Subtract
2*3 #Multiply
5/2 #Divide
5**2 #Exponent

#Name Error-This happens when there is a variablewith a name that the computer does not recognise. It's usually because you've misspelt the name of a variable you created earlier.
Note: variable names are case sensitive!
my_number = 4
my_Number + 2

#Zero Division Error-This happens when you try to divide by zero, This is something that is mathematically impossible so Python will also complain.
5 % 0

#Syntax Error-Syntax errors happen when your code does not make any sense to the computer.This can happen because you've misspelt something or there's too many brackets or a missing comma.
print(12 + 4))
SyntaxError: unmatched ')'

#Creating Functions- This is the basic syntax for a function in Python. It allows you to give a set of instructions a name, so you can trigger it multiple times without having to re-write or copy-paste it. The contents of the function must be indented to signal that it's inside.
def my_function():
print("Hello")
name = input("Your name:")
print("Hello")

#Calling Functions-You activate the function by calling it.This is simply done by writing the name of the function followed by a set of round brackets. This allows you to determine when to trigger the function and how many times.
my_function()
my_function()
#The function my_function will run twice.

#Variable Scope-Variables created inside a function are destroyed once the function has executed. The location (line of code) that you use a variable will determine its value.
Here n is 2 but inside my_function() n is 3.So printing n inside and outside the function will determine its value.
n = 2
def my_function():
n = 3
print(n)
print(n) #Prints 2
my_function() #Prints 3
#Functions with Outputs-In addition to inputs, a function can also have an output. The output value is proceeded by the keyword "return".This allows you to store the result from a function.
def add(n1, n2):
return n1 + n2
result = add(2, 3)

#Keyword Arguments-When calling a function, you can provide a keyword argument or simply just the value. Using a keyword argument means that you don't have to follow any order when providing the inputs.
def divide(n1, n2):
result = n1 / n2
#Option 1:
divide(10, 5)
#Option 2:
divide(n2=5, n1=10)

#C O N D I T I O N A L S = If-This is the basic syntax to test if a condition is true. If so, the indented code will be executed, if not it will be skipped.
n = 5
if n > 2:
print("Larger than 2")
#Else (this is a way to specify some code that will be executed if a condition is false.)
age = 18
if age > 16:
print("Can drive")
else:
print("Can't drive")
#not(This will flip the original result of the condition. e.g. if it was true then it's now false.)
if not 3 > 1:
print("something")
#Will not be printed. and this expects both conditions either side of the and to be true.
s = 58
if s < 60 and s > 50:
print("Your grade is C")
or
This expects either of the conditions either side of the or to be true. Basically, both conditions cannot be false.
age = 12
if age < 16 or age > 200:
print("Can't drive")

#comparison operators-These mathematical comparison operators allow you to refine your conditional checks.
> Greater than
< Lesser than
>= Greater than or equal to
<= Lesser than or equal to
== Is equal to
!= Is not equal to

_ in a For Loop-If the value your for loop is iterating through, e.g. the number in the range, or the item in the list is not needed, you can replace it with an underscore.
for _ in range(100):
#Do something 100 times.

#L O O P S
->While Loop-This is a loop that will keep repeating itself until the while condition becomes false.
n = 1
while n < 100:
n += 1
->For Loop-For loops give you more control than while loops. You can loop through anything that is iterable. e.g. a range, a list, a dictionary or tuple.
all_fruits = ["apple","banana", "orange"]
for fruit in all_fruits:
print(fruit)
->break-This keyword allows you to break free of the loop. You can use it in a for or while loop.
scores = [34, 67, 99, 105]
for s in scores:
if s > 100:
print("Invalid")
break
print(s)
->continue-This keyword allows you to skip this iteration of the loop and go to the next. The loop will still continue, but it will start from the top.
n = 0
while n < 100:
n += 1
if n % 2 == 0:
continue
print(n)
#Prints all the odd numbers
->Infinite Loops-Sometimes, the condition you are checking to see if the loop should continue never becomes false. In this case, the loop will continue for eternity (or until your computer stops it). This is more common with while loops.
while 5 > 1:
print("I'm a survivor)