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Pyhton Cheat Sheet by

Vocabulary

Variable
Hold a value and can be change
String
A list of character such as number, better and symbols
Integer number
Whole number/ counting number
Float number
The umber in decimal
Syntax
Gramma­r/S­tru­cture of language
Modulo
Find the remainder
Boolean
True/False

Addition

string­+string
combines the strings together
string­+number
crash
number­+number
math(a­ddi­tion)

Multip­lic­ation and Exponents

string* string
crash
string* number
combines the string multiple times
number* number
math(m­ult­iply)
string** number
crash
number** number
expone­nt(­math)
string** string
crash

Example

mylist3 = [1, 'hello', 2.3]

print (mylist)
print (mylist2)
print (mylist3)

#how to make a list with all number from 0-99

mynumbers = range(5)

for num in my numbers:
    print (num)

Example: Create function

def calc (num1,num2, operation) :
    if operation == "sum":
        return sum(num1,num2)
    elif operation == "product" :
        return product(num1,num2)
    elif operation == "diff" :
        return diff(num1,num2)
    elif operation == "div" :
        return div(num1,num2)
    
def sum (a, b) :
    return a + b
    
def product (a, b) :
    return a *b

def diff (a, b) :
    return a - b

def div (a, b) :
    if b != 0:
        return a /b
    else:
        print("Error")
    

print (calc(10, 0, "div"))

print (calc(1,2,"sum"))
print (calc(4,2,"diff"))
print (calc(9,3,"div"))
print (calc(2,12,"product"))

Maximum

write a function that returns the largest of two values
# name: max2
# arguments: num1, num2
# return: the largest value
def max2 (num1,num2):
    maxvalue = num1
    
    if num2 > maxvalue:
        maxvalue = num2
    return maxvalue

print (max2(3,4))

# write a function that returns the largest of three values
# name: max3
# arguments: num1, num2, num3
# return: the largest value

def max3 (num1,num2,num3):
    maxvalue = num1
    
    if num2 > maxvalue:
        maxvalue = num2
   
    if num3 > maxvalue:
        maxvalue = num3
        
    return maxvalue

print (max3(3,4,8))

# write a function that returns the largest number in a list
# name: maxlist
# argument: list
# returns the largest value in the list


def maxlist (list):
    maxvalue = list[0]
    for item in list:
        if item > maxvalue:
            maxvalue = item
            
    return maxvalue

list = [1,2,3,6,19,50,2,4,5]
print (maxlist(list))

Range()

#creates a list of numbers from 0 to the specified
number
numberlist = range(5)
# is the same as creating the following list
numberlist2 = [0, 1, 2, 3, 4]
for num in range(100):
    print (num) # prints all numbers from 0 – 99
for num in range(5, 50):
    print(num) #prints all numbers from 5 - 49

From Worksheet

Write a program that repeatedly receives positive integers from the user. When the user enters a negative integer, exit the loop an print how many of the number entered were odd and even.

evencount = 0
oddcount = 0
while True:
     user_input = int(input("Enter the number: "))
     if user_number < 0:
        print("Even: ",evencount)
        print("Odd: ",oddcount)
        break
     elif user_input > 0:
        if user_input % 2 ==0:#even
           evencount = evencount + 1
        else:
           oddcount = oddcount + 1

Even number from -100 to -1(While loop)

num = 0
while num > -100
   number = num -2
   print (num)

From worksheet

Determines that number is negative, positive or zero
Ex; 4 is positive / 0 is Zero / -8 is negative
user_num = input ("Enter the number")
user_num = int(user_num)
If user_num == 0
      print (user_num,"iszero")
elif user_num < 0:
      print (user_num," is negative")
elif user_num > 0:
      print( user_num, "is positive")

Write a functi­on(­mul­tip­lic­ation table)

def multipicationTable():
   user_input = int(input("Enter a number: ")
   num = 1
   while num <= 10 :
       print (user_input, "", "num", "=", "user_inputnum")
       num = num + 1
 

Functions

print()
Show inform­ation that you want on the screen
input()
Gain info from the user
int()
Change number to be number integer
float()
Change number to be decimal number
str()
All ;ist of number, letter and symbols
len()
The length of the string
#
Comment, no effect

Math

==
equal to
!=
no equal to
<
less than
>
more than
<=
less than or equal to
>=
more than or equal to
%
Modulo, Find the remainder

Reverse Word

while True:
word = input("Please enter word")
index = 0
reverse = ' '

while int(index)<len(word)
       reverse = word[index] + (reverse)
       index = int(index) + 1

print("Reverse:", reverse)

Import random

import random

intlist = [1,2,3,4,5]
random_int = random.choice(intlist)
print (intlist, random_int)

fplist = [1.5,2.5,3.5,4.5,5.5]
random_fp = random.choice(fplist)
print (fplist, random_fp)

strlist = ['1', '2', '3', '4', '5']
random_str = random.choice(strlist)
print (strlist, random_str)

mylist = [1, 2, 3, 4, 5, 1.5, 2.5, 3.5, 4.5, 5.5, '1', '2', '3', '4', '5']
random_item = random.choice(mylist)
print (mylist, random_item)

myvar1 = 1
myvar2 = 2
myvar3 = 3
varlist = [myvar1, myvar2, myvar3]
random_var = random.choice(varlist)
print (varlist, random_var)

Function call

def printDefinitions (word):
     if word == "variable":
        # variable
        print ("""
        a variable is are nothing but reserved memory locations to store values or something that can be change.
        """)
    elif word == "function":
        # function
        print ("""
        a function is the thing that define and put the code in there to reuse it again.
        """)
    elif word == "function call":
        #function call
        print ("""
        a function call is function that already have code and can use it.
        """)
    elif word == "parameter":
        #parameter
        print ("""
        a parameter is something that we put in function to define variable
        """)
    elif word == "argument":
        #argument
        print ("""
        a argument is the parameter.
        """)
    elif word == "string":
        #string
        print ("""
        a string is a letter.
        """)
    else:
         print ("Unknown word")

while True:
      user_input = input("Enter a word to define: ")
      printDefinitions(user_input) # function call

Forever While Loop

while True: # forever
      user_input = input('Enter a number: ')
      number = int(user_input)
      print ('The number squared is', number ** 2)

Decision Making­/Co­ndi­tional Statem­ents:

if 3 < 2: #if statement must compare two Booleans
    print ('3 is less than 2')
elif 4 < 2: #can have 0 or more elif statements
    print ('4 is less than 2')
elif 5 < 2:
   print ('5 is less than 2')
else: #can have 0 or 1 else statement at the end
   print ('none of the above are True')

Lists:

mylist = [2,3,4,5] # create a list
#select an item from a list
print (mylist[0]) #selects first item and displays 2
# len() determines the length of the list
print (len(mylist)) # displays 4
mylist.append(5) # adds an item to the end of the list

Exercise

'''1. Write a program that uses a for loop to print out all the items from a list
   called theList'''
theList = [1,2,3,4]
for item in theList:
    print(item)

'''2. Write a program that uses a while loop to print out all the items from a list
   called whileList'''
whileList=['bacon', 'cokezero', 'pepsi']
num = 0
while num < len(whileList):
    print(whileList[num])
    num = num + 1

'''3. Write a program that repeatedly accepts user input, prints out the length of
   whatever they type in and quits when the user enters the word 'exit' '''
while True:
    user_input = input('Enter a word: ')
    if user_input == 'exit':
        break
    else:
        print (len(user_input))

'''4. Create a function called theFunction, that has no parameters
and returns nothing. This function should repeatedly accept user input until
the user enters the word 'stop'. Call this function and run it.'''
def theFunction():
    while True:
        user_input = input('Enter a word: ')
        if user_input == 'stop':
            break
    return
#call the function(function call)
theFunction()

'''5. Create a function called computeThis, that takes two parameters, a1 and b2.
The function should return the product of both parameters. Call this function
and print the result.'''
def computeThis(a1, b2):
    return a1 * b2

print ("Product of 2 and 3 = ",computeThis(2,3))

'''6. Create a function called finalFunction, that has 1 argument called string.
The function should print the argument surrounded by "**" and return nothing.
Call this function. '''

def finalFunction(string):
    print ('*' + string + '*')

finalFunction('hello')
 

Naming Convention

Rule for giving name
- letter
- numbers
- underscore_
                      
Valid name
- _myStr
- my3
- Hello_there

Invalid name
- 3my="hi" --cannot start with number
- first name="hi'
- first-name

Convert to binary

user_number = ' '

while user_number != ' 0 ' :
      user_number = input("Enter a number to convert to binary")
      number = int(user_number)
      binary_string = ' '

while(number > 0):
       remainder = number%2
       binary_string = str(remainder)+ binary_string
       number = number/ /2
print("Binary string is", binary_string)
number = number/ / 2

print("Binary string is", binary_string)

Countdown Machine

user_number = input(:What number do you want to countdown?")
number = int(user_number)
countdown_string = ' '

while number > 0:
      countdown_number = countdown_string + str(number) + " "
      number = number - 1
#print(number)

print (countdown_string)

Example

Print (2) - integer
Print (2.5) - floating point
Print ("He­llo­") - string
Print (mystr) - variable
Print (mystr. "­Hi",­2,1.0) -- commas

mystr = "­Hi"
mystr ◀︎ name
"­Hi" ◀︎ value can change

mtstr (int(int)) ➤ 1
print (int("2­")) ➤ 2
print (float(1)) ➤ 1.0 anything to a float

Example

def myprint(text) : #mtvar is an argument (parameter) to he function
    print ("" + str(text) + "")
    return #return exists the function

myprint(1)
myprint(2.5)
myprint("hello")


def myprintnew(text, decoration) : #text and decoration are arguments to the function
    print (decoration + text + decoration)
    return

myprintnew("hello", "+++")
myprintnew("hello", "-=-=-=-=-=")
myprintnew("hello", ">>>>>>")



def doubleIt(number) :
    return number * 2 #return value

print (timesTwo(2))

myvar + timesTwo(timesTwo(3)) #same as timesTwo(6) bacuse timesTwo(3) == 6
print (myvar) # it will display 12



def areaOfCircle(r):

    if r <= 0:
        return "Error: invalid radius"
    
    pi = 3.1415
    area = pi r * 2
    return area

user_radius = float(input("Enter the radius: ")

print("The area of the circle is", areaOfCircle(user_radius))

Condit­ional While Loop

count = 0 # start at zero
while count < 10: # loop while count is less than 10
        print(count) #will print numbers 0 - 9
        count = count + 1 #must increase count

Printing values:

print("hello", "there") #displays hello there
print("hello" + "there") #displays hellothere

For‐Loop with List:

forlist = [3, 4, 5, 2, 1]
for item in forlist:
   print(item)

While Loop with List:

thelist = [4, 3, 2, 1, 0]
index = 0 # start at the first item
while index < len(thelist):
      print (thelist[index]) #prints each item
      index = index + 1

Comments

# hashtag – everything after # is a comment not code
"""
Double quote - Multi-line comment, everything in
between three double quotes is a comments
"""
''' Single quote - Multi-line comment, everything in
between three single quotes is a comments '''

From worksheet

0
01
012
0123
01234
mystring = " "
count = 0
while count < 5:
    mystring = mystring + str(count0
    print (mystring)
    count = count + 1

From worksheet

Use a for loop to print the following:
0
012
0123
01234

mystring = ""
for num in range(5)
     mystring = mystring + str(num)
     print (mystring)

From worksheet

Create a program to receive a number from the user and determine if that number is divisible by3.
Example:
- 9 is divisible by 3.
- 7 is not divisible by 3.

user_num = int(input("Enter the number: "))
if user_num%3 == 0:
   print(user_num, "is divisible by 3")
else:
   print(user_num, " is not divisible by 3")

Print all items in the list

Give a list called mylist, print all items in the list using a loop.
mylist = [1,2,3,4]
for item in mylist:
    print (mylist)

Another method
num = 0
while num < len(mylist)
     print(mylist[num])
     num = num + 1

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Comments

memfail memfail, 04:48 4 Jan 19

Hi Warisara, nice work. Please fix title - Python is spelled incorrectly. Thanks.

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