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# Pyhton Cheat Sheet by warisara

### 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     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)

### 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) #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

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

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