Python General Revision

Question 1

data type

Answer 1

numbers, text, booleens etc

Question 2

whitespace

Answer 2

seperates statements

whitespace means right space

Question 3

comments

Answer 3

to make code easier to follow
# for single line comment
“"”for multi line comments”””

Question 4

boolean

Answer 4

true or false statements

variables can store booleans
ie: a = true
b = false

Question 5

Python order of operation

maths PEMDAS

Answer 5

python uses PEMDAS system:
Parentheses ( …) = everything in brackets first
Exponents ** = powers (5 ^ 3 is 5x5x5). written as 5 ** 5 in python
Multiplication
Division
Addition, Subtraction

Question 6

modulo (Mod)

Answer 6

modulo returns the remainder from a division.

ie. 3%2 will return 1. 2 goes into 3 once with 1 remaining (remember the remaider is the bit modulo is interested in)

Question 7

String

Answer 7

A string is a data type which is written in “quotation marks” ie “ryan”
It can contain numbers, letters and symbols.
Each character in a string is assigned a number (the index) starting with 0.

Question 8

String method

Answer 8

lets you perform specific tasks for strings ie:
len() = length of string
str() = turns non-string into string ie. str(2) into “2”
. lower() = makes string all lowercase ie. “Ryan” .lower() into “ryan”
. upper() = makes string all uppercase

Question 9

Dot Notation

Answer 9

this is strings with dot notation in!
ie “Ryan” .upper() or “Ryan”.lower()
but it could be one of many dot .() commands

Question 10

String Concatenation

Answer 10

This is combining strings with math operators

ie print “life + of + brian” becomes life of brian

Question 11

Explicit String Conversion

Answer 11

converts non string to string ie:
print “I have” + str(2) + “coconuts!”
will print
I have 2 coconuts!

Question 12

String Formatting

Answer 12

printing a variable with a string
%s goes in the string
% goes after string
string1 = "Camelot"
string2 = "place"
print "let's not go to %s tis a silly %s" % (string1, string2)

Question 13

3 ways to create string

Answer 13

‘Ryan’
“Ryan”
str(2)

Question 14

1. print a string

2. advanced printing

Answer 14

1. print “Hello” Hello
2. g = “golf”
   h = “hotel”
   print “%s, %s” % (g, h)golf hotel

Question 15

datetime

datetime.now

Answer 15

datetime is a type of data (date and time).

datetime.now prints current date and time

Question 16

from command

import command

Answer 16

from = data location

import = get data

Question 17

hot commands and placeholders

in printing datetime context

Answer 17

placeholder = %s       hot command = %
from datetime import datetime
now = datetime.now()
print '%s/%s/%s %s:%s:%s' % (now.day, now.month, now.year, now.hour, now.minute, now.second)                  
08/08/2014 13:56:23

Question 18

Control Flow

Answer 18

Enables code to make decisions

Question 19

Control Flow: Comparators

Answer 19

equal to ==       
not equal to !=      
less than <      
greater than >
less than or equal to =

Question 20

Control Flow: Expressions

Answer 20

expressions are values that can have operations like maths, boolean, if, or, and, not, nor, nand, etc.

18 >= 16
extreme expressions and comparators
(10 + 17) == 3 ** 16

Question 21

Control Flow: Boolean operators

Answer 21

not and or
not is calulated 1st
and is 2nd
or is last

true or false (3 < 4) and (5 >= 5) this() and not that()

Question 22

Control Flow: Conditional statements

Answer 22

if       elif        else                   OR   def chess_game_score (answer):
if this_might_be_true():                          if (answer) > 5:
     print "this is true"                                             return "true"
elif that_might_be_true():                       elif (answer) (3 < 4) and (5 >= 5):
     print "this is really true"                                    return "false"
else:                                                        else: 
     print "none of the above"                                 return "neither"

Question 23

.isalpha

Answer 23

checks strings for non letters

Question 24

what does a comma do in a print statement of variables?
eg
variable_1 = "hello"
variable 2 = "chris"
print variable_1, variable_2

Answer 24

creates a space between variable strings
eg it will print this
hello chris

Question 25

how do you write a variable with a string of placeholders then set the data type or value of those place holders in the print statement?

Answer 25

chris = “ %r %r %r”

print chris % (“25”, “years”, “old”)

25 years old

Question 26

what does \n do in front of data types in a string?

Answer 26

\n creates a new line between each data type in a string
eg:
variable_1 = “\nchris\ngareth\njason
print variable_1

chris
gareth
jason

Question 27

what does using “”” instead of “ at the beginning and end of a string allow you to do?

Answer 27

It allows you to print data on continues lines.

print
“"”do this, do that, do nothing.
do something, do everything
dont do anything at all!”””

do this, do that, do nothing.
do something, do everything
dont do anything at all!

Question 28

what does the raw_input command do?

Answer 28

enables user to input text
enables program to get data and data types from a user
enable program to use this data in program
enable program to print a string of data to user based on that input

Question 29

what is pydoc?

Answer 29

pydoc is pythons documentation module which allows programmers to acces help files, generate html pages with doc specifics and find appropriate modules for particular jobs

Question 30

what is a script?

Answer 30

another name for a .py file type

Question 31

what is an argument?

Answer 31

another name for a file name

Question 32

what does an argv function do?

Answer 32

the in built function argument variable calls/runs variables assigned to it that relate to file names and types/formats

from sys import argv
script, input_file = argv

so if i now typed ‘python exp20c.py test.txt’ in command line the code above would run both files. specifically it would run the program on the python file exp20c.py (script) and run it on the file test.txt (input_file)

Question 33

what are modules?

Answer 33

Features you import to make your python program do more.

also called libraries

Question 34

open

Answer 34

opens file

Question 35

how to give files commands

Answer 35

put a . after file or variable name

txt = open(filename)
print txt.read

txt is a variable which opens a file. print txt.read tells program to read that files text and print it.

Question 36

function and method are other names used for?

Answer 36

a command

Question 37

what is a command

Answer 37

instruction to program to do something with a file
eg open, print, read

read command reads data in a given file and when combined with the print command will print it ( print txt.read)

Question 38

Reading and writing files

What do close, read, readline, truncate and write commands do?

Answer 38

close = save and close ("c")
read = read data from file ("r")
readline = read just one line of data from a file 
truncate = empties file. delete all dat in file
write = write data to file

can be added as an extra parametre
eg target = open(filename, “w”)
this mean open file in write mode (as opposed to read mode)

Question 39

do you need a truncate command when using a write command?

Answer 39

no, write command will overwrite data in file so no need for truncate (erase file contents) command.

Question 40

what are packages?

Answer 40

directories (folders)

Question 41

what are modules?

Answer 41

files
You know that a module is a Python file with some functions or variables in it.
2. You then import that file.
3. And then you can access the functions or variables in that module with the '.' (dot) operator.
 In the case of the module the key is an identifier, and the syntax is .key. In the case of the dictionary, the key is a string and the syntax is [key].Other than that, they are nearly the same thing.

mystuff[‘apple’] # get apple from dict mystuff.apple() # get apple from the module mystuff.tangerine # same thing, it’s just a variable

Question 42

what are modules?

Answer 42

files, arguments
A way to think about a module is that it is a specialized dictionary that can store Python code so you can get to it with the '.' operator. 
You know that a module is a Python file with some functions or variables in it.
2. You then import that file.
3. And then you can access the functions or variables in that module with the '.' (dot) operator.
 In the case of the module the key is an identifier, and the syntax is .key. In the case of the dictionary, the key is a string and the syntax is [key].Other than that, they are nearly the same thing.

mystuff[‘apple’] # get apple from dict mystuff.apple() # get apple from the module mystuff.tangerine # same thing, it’s just a variable

Question 43

why is closing files at end of code important?

Answer 43

close command not only closes file but saves it too.
having lots of open file is not good, there is also a limit to amount of open files at same time.
good practice.

Question 44

files are also known as

Answer 44

modules, arguments

Question 45

what does close command do?

Answer 45

closes and saves files

output_file.close

Question 46

what does exists command do?

Answer 46

looks for a specified file and return True statement if it already exists, and False if it doesnt.

Question 47

what is os.path?

Answer 47

a location on computer containing modules (files) of useful commands to use in programming.

Question 48

what 3 things do functions do?

Answer 48

1. they are commands/methods that call/run sub-routines!!!
2. they take arguments the way scripts take argv
3. they use both the above to enable you to make ‘mini scripts’ or ‘tiny commands’.
4. names a peice ???of the way variable name strings and numbers

Question 49

what are definitions? def

Answer 49

1. a definition is a keyword that assigns a subroutine with a function or command to a variable.
2. it must end its first command line with :
3. the def variable can have other variables as parameters that it can call/run. def variable_1(variable_2, variable_3):
   the subroutine of a def must be indented so the program knows that any code that is indented is part of that subroutine.
   def variable_1(variable_2, variable_3):
   print variable_2, variable_3.read()

Question 50

truth tables for NOT, OR, AND, NOR, NAND

Answer 50

NOT: not false = true, not true = false 0=1 1=0
OR: false or false = false 0 or 0 = 0
NOR: false and false = true 0 or 0 = 1
AND:true and true = true 1 and 1 = 1
NAND: true and true = false 1 and 1 = 0

Question 51

==

!=

Answer 51

equal to 1 == 1 is true 1 == 0 is false

not equal to 1 != 1 is false 1 != 0 is true

Question 52

a += 1
a -= 1
a *= 1
a /= 1

Answer 52

a = a + 1
a = a - 1
a = a * 1
a = a / 1

Question 53

if statements and how they work.

Answer 53

if, elif and else
logic decision that create branches that can:
make decisions themselves
make decision themselves and direct to specified areas of program or to sub routines or other branches (if statements)

Question 54

nests

Answer 54

if statements within if statements

or branches within branches

Question 55

what are lists?

Answer 55

containers that store data types in an organised manner
data types in lists are assign values starting at 0 (cardinal)
you can then use these values/numbers to index into a list to find specific data.
you can only use number to index
If you need to maintain order. Remember, this is listed order, not sorted order. Lists do not sort for you.
If you need to access the contents randomly by a number. Remember, this is using cardinal numbers starting at 0.
If you need to go through the contents linearly (first to last). Remember, that’s what for-loops are for.

Question 56

.append

Answer 56

command that adds something to the end

Question 57

what are lists?

Answer 57

containers that store data types in an organised manner
data types in lists are assign numeric values starting at 0 (cardinal)
you can only use numbers to index into a list to find and retrieve specific data.
The order you put things in list is the number order for retrieval. Remember, this is listed order, not sorted order. Lists do not sort for you.

you can access contents randomly or specifically anywhere in the list by using numbers
use a for-loop to go through the contents linearly (first to last).

Question 58

while-loop function

Answer 58

loops through list till an assigned criteria is met

while i < 6:
print “not yet”

Question 59

what are def, for and while?

Answer 59

def, for and while are keywords that call sub routines

Question 60

floating point method

Answer 60

approximation of a real number that can support a wider range of values
Basically this is using averages to represent a number
ie:
range for a number (difference between smallest and largest number)
median (the middle number in a range [number need to be put in order first])
mode (the number repeated most often in a range)
mean (the average number in a range)

Question 61

fixed point method

Answer 61

represents a real data type for a number with fixed digits before and after a decimal point
it is an integer (int)
it always have a parameter/factor attached to it most commonly an exponent or power of 10 or 2
20 ** 2
20 ** 10

Question 62

base 2

Answer 62

a binary numeric value

think computer maths logic

Question 63

base 10

Answer 63

a decimal numeric value

think human maths logic

Question 64

hexadecimal or base 16

Answer 64

counting system commonly used in programming using a 16 digit scale:
hex 0123456789 a b c d e f
dec 0123456789101112 13 14 15
written as ‘0x’ in code

Question 65

ASCII

Answer 65

english language characters

Question 66

Unicode

Answer 66

universal code
multi language characters

UTF-8
1 byte = standard ASCII
2 bytes = Arabic, Hebrew and most European scripts
3 bytes = BMP
4 bytes = All Unicode characters

Question 67

concatenation

Answer 67

joining strings together

“snow” “ball” becomes “snowball”

Question 68

OOP

Answer 68

Object-oriented programming (OOP) is a programming paradigm that represents the concept of “objects” that have data fields (attributes that describe the object) and associated procedures known as methods.

Objects, which are usually instances of classes, are used to interact with one another to design applications and computer programs.[1][2] C++, Objective-C, Smalltalk, Delphi, Java, Javascript, C#, Perl, Python, Ruby and PHP are examples of object-oriented programming languages.

Question 69

instances

Answer 69

??

Question 70

Variable

Answer 70

A CONTAINER that stores data/values as a specific name

ie spam = 5

Question 71

class

Answer 71

Classes Are Like Mini-Modules

A class is a way to take a grouping of functions and data and place them inside a container so you can access them with the ‘.’ (dot) operator.

A container for objects, functions , data.

class song(object):

def \_\_init\_\_(self, lyrics):

when assigning an object as a parameter of a class, the first parameter variable of __init__ becomes object. the word self is used as good practice, however it is just a variable and can be called anything you want.

Question 72

objects

Answer 72

Objects Are Like Mini-Imports

If a class is like a “mini-module,” then there has to be a similar concept to import but for classes. That concept is called “instantiate,” which is just a fancy, obnoxious, overly smart way to say “create.” When you instantiate a class, what you get is called an object.

The way you do this is you call the class like it’s a function, like this:
thing = MyStuff() 
thing.apple()
print thing.tangerine

Question 73

Dictionaries

Answer 73

In python called dicts (hashes in other languages).
It maps one data type/item (called keys) to another data type/item (called values). (like in a dictionary maps a word to its definition)
In the case of the dictionary, the key is a string and the syntax is [key]. In the case of the module the key is an identifier, and the syntax is .key. Other than that, they are nearly the same thing.

Are a type of data structure like lists.
Unlike lists dicts allow you to index/locate data with anything not just numbers.
It associates one thing with another.
{ } brackets.
Dictionaries allow you to add things to them in other parts of your program.
They also allow you to delete things from them.
They can have numbers as parameters in [ ] that are assigned to them as printable.

mystuff[‘apple’] # get apple from dict mystuff.apple() # get apple from the module mystuff.tangerine # same thing, it’s just a variable

Question 74

cardinal numbers start at 1 or 0?

Answer 74

0

Question 75

index

Answer 75

the assignment of numeric values to data.
usually used in lists etc where each bit of data in the its has a number assigned to it. this is assigned in the order data is in the list using cardinal numbering system.

Question 76

delete items from a list

Answer 76

del stuff[1]

Question 77

delete items from a dict

Answer 77

del stuff[‘city’]

Question 78

getting things from classes

Answer 78

thing = MyStuff()
thing.apples()
print thing.tangerine

Question 79

getting things from modules

Answer 79

mystuff.apples()

print mystuff.tangerine

Question 80

getting things from dicts

Answer 80

mystuff[‘apples’]

Question 81

(variable1, variable2 )

Answer 81

variables as parameters

Question 82

([‘apple’, ‘cheese’, biscuit’ ])

Answer 82

lists as parameters

Question 83

(“hello silly”, “cheese please”)

Answer 83

strings as parameters

Question 84

(10, 2)

Answer 84

numbers as parameters