前言

下面內容來自ED，Week12，小編會以筆記的方式去講解，如有錯誤及時聯系我及時更正，爭取在11月26號（周四）之前完成，

Review :

1. Iterator vs Iterable

iterator: stream of data
iterable: sequence that you can iterate through
講解： iterator中文意思為迭代器，表示資料流的物件，iterable中文意識是可迭代，一個能夠一次回傳其成員的物件

資料鏈接1： iterator 和 iterable的關系
資料鏈接2： iterator 和 iterable的解釋

2.True or False: local variables only exist within the scope of a function

def function():
    a = 5 #local variable 
print(a) #NameError

Answer： True

講解： 標題意思為區域變數僅存在于函式范圍內，判斷是否正確，首先我們要了解什么是Local variable.中文意思為區域變數，在函式體內或區域范圍內宣告的變數稱為區域變數，
上面程式中的a=5就是local variable，在自定義函式范圍內運行，如果跳出函式，運行時就會報錯為’NameError: name ‘a’ is not defined‘，

local variable 解釋： local variable 講解

3.What is a pure function (week 5 lab sheet)

function with no side effect

講解： 問什么是pure function，中文意思為純函式，一個純粹的功能不會產生副作用，
pure function解釋： pure function 的解釋
解釋2： pure function

4.What are side effects of a function( week 5 lab sheet)

modifying data that are passed in or global variables (use global)

a = 5
def function():
    print(a) #can read global variable 
    
    #modify global variable
    global a
    a += 1

解釋： 問題問功能的副作用是什么（沒必要記住中文什么意思，中文只是輔助記憶，主要還得是英文）？修改傳入的資料或全域變數（使用全域）

很細致的講解side effects of a function： side effects鏈接
Side Effects講解： Side Effects
Side Effects in Python： Side Effects in Python
ED課件講解： week5lab_5.0_part4 (登錄ed后能看見）

5.What is initializing

assigning value to a variable

解釋： 什么是初始化，給變數賦值，（可能__init__就是初始化，下面鏈接里有詳細資料），
Initializing variable in python: Initializing

6.What is declaring a variable

creating the variable

a = True
b = False

a and b -> True and False -> False
a or b -> True or False -> True
a and b or a -> True and False or True -> False or True -> True
a or b or c -> True or False or ? -> True or ? -> True because of short circuit
a and b or c -> False or c -> NameError
a and b and c -> False and c ->  False because of short circuit

1. ()
2. not
3. and
4. or

解釋： 什么是變數宣告，就是創建變數，a為True，b為False， 如果有and表示都正確，運行，遇到false整個條件判斷為false，or 就是兩者有一個為true就可以運行，
declearing variable: Python Variable
python variable declaration: variable

7.What is the difference between == and is

is : always compare the memory address
== : values unless you’re dealing with object
"hello" == "hello"
解釋： 問==和is在程式里的區別，is是判斷兩者是否參考同一個物件（參考地址），==是判斷兩者的值是否相等，
is ==用法： 兩者用法鏈接
difference: 不同用處

8.What are the advantages of using if-elif-else rather than a bunch of if statements

if a == 5:
    do something
if a == 6:
    do something
if a == 7:
    do something

if a == 5:
    do something
elif a == 6:
    do something
elif a == 7:
    do something

this one is faster
解釋： 問用if-elif-else而不用if-if-if的好處，程式運行的更快捷，前者程式要檢查每一個if模塊，后者直接條件判斷，
if-elif-else用法： 菜鳥教程的用法-中文
用法教程： Programiz的用法-英文

What is a flow chart
chart describing flow / structure of the code
contains diamonds (decisions) and rectangles

What is a desk check
keep track of how variables changes throughout program
use it for debugging
make sure you have a column for every variable and one for output

What datatype is mutable in python
list, class, dictionary

What datatype is iterable in python
list, dictionary, iterators

dict = {"key":[], "key2":"value"}

What is the difference between []*5 vs [0]*5
length of []*5: 0
length of [0]*5: 5

a = [1,2, 3, 4, 5, 6]
for i in a:
    i += 1

What does a store at the end of this code snippet?
no. for loops are read only

a = [1,2, 3, 4, 5, 6]
for i in range(len(a)):
    a[i] += 1

Describe the differences between black box testing and white box testing
white box: sees code
end to end is black box?

What is a module lecture 14 slide 4
sys, math, random
predefined code / program that allows you to do …
import the modules so you can use the functionalities inside

How do you modify a global variable in Python
global

True or False, you always have to close a file after reading or writing them. If not, when can you get away with it?

f = open("text.txt")
df = f.readlines()

file isn’t closed, file could be corrupted

with open("text.txt") as f:
    df = f.readlines()

Python close automatically

What is sys.stdout?
sys.stdout == print

True or False: Tuples are mutable
False

f = (1, 2, 3)
f = (2, 3, 4)

this one is actually pointing to a different address entirely

How do you do x^4 in Python without importing Math module?
x**4

True or False: A function does not have to return anything
False because a function always returns None when user doesn’t define a return

True or False: A tuple can vary in size

a = (1, 2, 3)
a = (1, 2, 3, 4) #works 
a.append(5) #this won't work because tuples are immutable

No a tupe cannot vary in size unless change memory location

Describe the differences in lists and arrays
lists : separately but they contain address of the next element , can vary in datatype, can change in size (use append)
arrays : stored together, can only have one datatype, can’t change size, can jump from one element to another

What happens when you try to create an object from a class that doesn’t have a pre-defined constructor?
a blank constructor is generated in background

By default, what gets printed when you print an object?
if didn’t write __str__() : <datatype, memory>
after writing __str__(): prints out the output you define

By default, what does Python compare when you compare two objects?
if didn’t write __eq__(): compares memory address
if you did write __eq__() : this one compares the variables that you define

What is the difference between static, class and instance methods?
instance : self, referring to the instance
class : cls, refers to the whole class, one change can change it for every instance of the class
static : doesn’t take in anything in parameter,

True or False: A function can have multiple returns
True

def function(a): #a is a boolean
    if a:
        return True
    else:
        return False

Why is testing important?
to make sure your code is running as it should
types of testing : end to end, unit testing, integration testing
black box, white box

What is integration testing?
checking whether connection of two or more systems are working

How do you perform end-to-end testing?
diff ____ ____

What is regression testing?
testing every test cases (previous and current phases) as you progress through the solution

總結

提示：最近期末，作業多 任務多，我會盡快更新，