通常都會把需要 import 的 module 們列在整個檔案的最一開始，但不是必須。

語法1：import [module]
帶入整組module
call function 的時候需要將module name一併鍵入=>module_name.function

# Import 整個 `random` module
>>> import random

# 使用 `random` module 底下的 `randint` function
>>> print(random.randint(0, 5))

語法3：import [module] as [new_name]
帶入整組module，並在程式中改以新定義的名稱(new_name)呼叫該module
call function 的時候需要將在import時新定義的module name一併鍵入=>new_name.function

# Import 整個 `random` module，
# 但這個名字可能跟其他地方有衝突，因此改名成 `rd` 
>>> import random as rd

# 使用 `rd` 這個名稱取代原本的 `random`
>>> print(rd.randint(0, 5))

語法2：from [module] import [name1, name2, ...]
僅帶入module中的特定function
呼叫該function之前不需要鍵入module name，直接呼叫function name

# 從 `random` module 裡 import 其中一個 function `randint`
>>> from random import randint

# 不一樣的是，使用 `randint` 的時候就不需要先寫 `random` 了
>>> print(randint(0, 5))

參考資料來源：
https://medium.com/pyladies-taiwan/3538e74f57e3

import 基本語法筆記 was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

>>>x = 6
>>>def func():
>>> global x
>>> x = 1
>>>
>>>func()
>>>print x
1

The keyword global is only useful to change or create global variables in a local context, although creating global variables is seldom considered a good solution.

>>>def bob():
>>>    me = "locally defined"    
>>> 　　# Defined only in local context
>>>    print me

>>>bob()
>>>print me     
>>># Asking for a global variable

locally defined
Traceback (most recent call last):
  File "file.py", line 9, in <module>
    print me
NameError: name 'me' is not defined

While if you use the global statement, the variable will become available "outside" the scope of the function, effectively becoming a global variable.

在function區去中宣告global變數，執行該function之後，即可於function之外讀取該global變數

>>>def bob():
>>>    global me
>>>    me = "locally defined"   
>>>    # Defined locally but declared as global
>>>    print me

>>>bob()
>>>print me     
>>># Asking for a global variable

locally defined
locally defined

global was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

若接著 SELECT DISTINCT 後面有指定兩個以上的欄位，則要符合所有選取欄位值皆同樣重複的情況下，該筆資料才會被捨棄不選取。
若只有其中一個欄位值相同但其它欄位值並不同，則仍會取出該筆資料。

參考資料來源：
https://www.fooish.com/sql/distinct.html
https://www.1keydata.com/tw/sql/sqldistinct.html

SELECT DISTINCT was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

continue 中止當前的循環，跳過該次循環中剩餘未執行的指令，接續執行次一個循環

break, continue was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

myjob= 'hacker'
for c in myjob: print (c, end='')
#output 
h a c k e r

print (end='') was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

課程：course 5(Capstone: Retrieving, Processing, and Visualizing Data with Python)
進度：week 2 ( Building a Search Engine)

import sqlite3

import sqlite3 導入sqlite3套件

conn = sqlite3.connect(‘spider.sqlite’) 建立一個名為‘spider.sqlite’的檔案

cur = conn.cursor() 建立一個cursor物件

完成cursor物件的建立之後，即可開始執行execute()

# Create table
cur.execute('''CREATE TABLE stocks
(date text, trans text, symbol text, qty real, price real)''')

# Insert a row of data
cur.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)")

# Save (commit) the changes
conn.commit()

# We can also close the connection if we are done with it.
# Just be sure any changes have been committed or they will be lost.
conn.close()

參考資料來源：https://docs.python.org/3/library/sqlite3.html#

cursor() 及 execute() was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

課程：course 5(Capstone: Retrieving, Processing, and Visualizing Data with Python)
進度：week 2 ( Building a Search Engine)

urllib是一個用來處理url的套件

• urllib.request：打開和讀寫urls
• urllib.error：定義由urllib.request引起的異常
• urllib.parse：解析urls(包含網址解析及網址引用)
• urllib.robotparse：分析robots.txt文件

urllib.request.urlopen(url, data=None, [timeout, ]*, cafile=None, capath=None, cadefault=False, context=None)

打開url

在urlopen()的功能下可使用以下method

• geturl() — return the URL of the resource retrieved, commonly used to determine if a redirect was followed
• info() — return the meta-information of the page, such as headers, in the form of an email.message_from_string() instance (see Quick Reference to HTTP Headers)
• getcode() – return the HTTP status code of the response.

參考資料來源：https://docs.python.org/3/library/urllib.request.html

urllib.parse. urlparse (urlstring, scheme=’’, allow_fragments=True)

將一組url解析為6個單元

>>> from urllib.parse import urlparse
>>> o = urlparse('http://www.cwi.nl:80/%7Eguido/Python.html')
>>> o   
ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='', query='', fragment='')
>>> o.scheme
'http'
>>> o.port
80
>>> o.geturl()
'http://www.cwi.nl:80/%7Eguido/Python.html'

參考資料來源：https://docs.python.org/3/library/urllib.parse.html

urllib.parse.urljoin(base, url, allow_fragments=True)

將兩組url結合為一個完整的位址

>>> from urllib.parse import urljoin
>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html', 'FAQ.html')
'http://www.cwi.nl/%7Eguido/FAQ.html'

參考資料來源：https://docs.python.org/3/library/urllib.parse.html

Urllib套件 was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

課程：course 4 (Using Databases with Python)
進度：week 4 (Many-to-Many Relationships in SQL)

PRIMARY KEY

primary key用來保證欄位在資料表中的唯一性，主鍵欄位中的每一筆資料在資料表中都必需是獨一無二的。

primary key 是該table 中具有唯一性與識別性的資料，若沒有單一資料具有此特性，也可以是兩個以上的資料合成具有此特性的key 值，即可做為primary key。

一個資料表中只能有一個 PRIMARY KEY。

CREATE TABLE User (
    id     INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
    name   TEXT UNIQUE
);

CREATE TABLE Course (
    id     INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
    title  TEXT UNIQUE
);

CREATE TABLE Member (
    user_id     INTEGER,
    course_id   INTEGER,
    role        INTEGER,
    PRIMARY KEY (user_id, course_id, role)
)

在Member這個表中，PRIMARY KEY (user_id, course_id, role)表示每一種(user_id, course_id, role)的組合皆為唯一
即，一個學生(user_id)只會以一種身分(role)參與在課堂之中(course_id)

PRIMARY KEY was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.

課程：course 5(Capstone: Retrieving, Processing, and Visualizing Data with Python)
進度：week 2 ( Building a Search Engine)

python3 + urllib套件

1. 立document為一虛擬變數，以urlopen()指令讀取url網址

document = urlopen(url, context=ctx)

2. 以getcode()讀取document的內容

document.getcode()

3.如getcode()回傳值為200，即網頁讀取成功；如為200以外的值，表示讀取不成功

HTTP 狀態碼表明一個 HTTP 要求是否已經被完成。
回應分為五種：資訊回應、成功回應、重定向、用戶端錯誤及伺服器端錯誤。

成功回應

200 OK請求成功。
成功的意義依照 HTTP 方法而定：
GET: 資源成功獲取並於 message body 內發送。
HEAD: entity 標頭已於 message body 內。
POST: 已傳送 message body 內的 resource describing the result of the action。
TRACE: 伺服器已接收到 message body 內含的請求訊息。

用戶端錯誤回應

403 Forbidden
用戶端並無訪問權限，所以伺服器給予應有的回應。
404 Not Found
伺服器找不到請求的資源。因為在 web 上它很常出現，這回應碼也許最為人所悉。

延伸閱讀：

1. urllib的使用方式 https://docs.python.org.tw/3/howto/urllib2.html
2. HTTP狀態碼 https://developer.mozilla.org/zh-TW/docs/Web/HTTP/Status

以getcode()查詢HTTP 狀態碼 was originally published in A beginner’s python notes on Medium, where people are continuing the conversation by highlighting and responding to this story.