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Python Sheet Cheat Sheet by

Vocabulary

variable
something that can change
string
a list of characters
loop
infinite playing
integer number
full number
float number
decimal number
print
shoe the output
syntax
gramma­r/s­tru­cture of language
modulo
find the remainder
boolean
true/false
function
a piece of code in a program
function call
telling that program to excute that function
parameter
something you gave to the function
argument
parameter

Code

input()
gain inform­ation for user
int ()
change number to be integer number
float ()
change number to be decimal number
str ()
a list of number, letter and symbols
print ()
show the result
len()
the length of the string
#
comment, no effect

Math

==
equal to
!=
not equal to
<
less than
>
more than
<=
less than or equal to
>=
more than or equal to
%
modulo, find the remainder

Multip­lic­ation & Exponent

string * number
combine the string
number * number
multip­ly(­math)
number ** number
expone­nt(­math)

Addition

string + string
combine together
number + number
additi­on(­math)

CRASH!

string + number
CRASH!
string * string
CRASH!
string ** string
CRASH!

True/False

True or anything is always TRUE
False and anything is always FALSE
 

Forever While Loop

while True:
      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 2 Boolean\
     print('3 is less than 2')
elif 4 < 2: #can't have 0 or more elif statement
     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')

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

For‐Loop with List

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

Functions

#function with no parameters/arguments
#and no return value
#return is optional if you do not return a value
def nameOfFunction():
    print (‘This function has no parameters’)
    print (‘This function has no return value’)
    return # no value, just exits the function
                        ______________________________________
#function call
nameOfFunction()
#function with 1 parameter/argument
def testFunction(param):
    print (‘This function has 1 parameter’)
    print (param)

#function call
testFunction (“this is the parameter value”) ______________________________________
#function with 2 parameters and a return value
def function3(param1, param2):
    print(‘This function has 2 parameters’)
    return param1 + param2 # return value
#function call and store the result in a variable
returnValue = function3(2, 3)
print (returnValue)

Count Even&Odd #

#repeatly receives positive integers from user and exit when gets negative number, then count even and odd number

evenCount = 0
oddCount = 0

while True:
     user_input = int(input("Enter number: "))
     if user_input < 0:
         print("Total even: ",evenCount)
         print("Total odd: ",oddCount)
         break
elif user_input > 0:
     if user_input % 2 == 0:
         evenCount = evenCount + 1
     else:
         oddCOunt = oddCount +1

Mystring

' ' '
expected output:
0
01
012
0123
01234
' ' '
mystring = " "
count = 0
while count < 5:
     mystring = mystring + str(count)
     print(mrstring)
     count = count + 1

Condition While Loop

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

Countdown Machine

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

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

print(countdown_string)

Random List

import random

#create a list
mylist = [-1,1.2,11,"srujryju","yikjghk"]
random_item = random.choice(mylist)
print(mylist, random_item)

Reverse Word

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

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

print ("Reverse: ", reverse)

Function pir*2

def areaoscircle(r):
      pi = 3.1415
      return pi r * 2
 

Printing values

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

Combining Strings (Conca­ten­ation)

"­hi" + "­the­re" == "­hit­her­e"
"­hi" * 5 == "­hih­ihi­hih­i"

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
- first+name

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

print(­int­(1.5)) -> 1
print(­int­("2")) -> 2
print(­flo­at(1)) -> 1.0 anything to a float

Example Code

mylist = [1, 'hello', 2.5]

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

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

mynumbers = range(5)

for num on mynumbers:
print (num)

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