今天有想在這裡分享 Regular Expression，這也是大家不想碰到的，可就是一個很復雜的就越耗用。
我也沒有很勵害，但之前開發自動化，用很多。因此想藉由這編文章來寫下我所寫道的筆記和參考很多教學。

在介紹之前我們在 python 都會用到 re 或是 rex ，但在這我只會分享用 re，也就是要 import re，不然不能用。

常用的 req module

compile()

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import re
text ='https://chenchih.page , Author is ChenChih'
pattern=re.compile('Chenchih',re.I)
print(pattern.match(text)) #None
print(pattern.search(text).group()) #chenchih
print(pattern.findall(text)) #['chenchih', 'ChenChih']

output:

None
cheenchih > > ['chenchih', 'ChenChih']

match()

This function matches a regular expression pattern at the beginning of a string. If the pattern is found, it returns a match object, otherwise, it returns None.

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import re
teststring="123abc456789abc123ABC"
pattern=re.compile(r"abc")
match=pattern.match(teststring)
print(match)

我想分享一些基本的DB(MYSQL)語法。之前面試有考不管是在Amazon，或Microsoft 都有考過我DB。我那時有準備筆記，但後來就不知跑哪。今天想在這篇寫關於SQL基本指令，有機會再寫高階的語法。

我住前是用MYSQL的DB軟體，你們可以選用其他的如MogoDB, Microsoft SQL server，orlacle DB等等。基本上語法都差不多，我猜的

• Table: employee:

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  +----+-------+--------+--------------+ | id | Name | Salary | DepartmentID | +----+-------+--------+--------------+ | 1 | Joe | 85000 | 1 | | 2 | Henry | 80000 | 2 | | 3 | Sam | 60000 | 1 | | 4 | Max | 90000 | 1 | | 5 | Janet | 69000 | 1 | | 6 | Randy | 85000 | 1 | +----+-------+--------+--------------+

SELECT & FROM

select * from

select 可以選擇要印那一欄，如果加*可以把所有內如印出來，以下是指令:

select * from employee;

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Table: employee;
+----+-------+--------+--------------+
| id | Name  | Salary | DepartmentID |
+----+-------+--------+--------------+
|  1 | Joe   | 85000  | 1            |
|  2 | Henry | 80000  | 2            |
|  3 | Sam   | 60000  | 1            |
|  4 | Max   | 90000  | 1            |
|  5 | Janet | 69000  | 1            |
|  6 | Randy | 85000  | 1            |
+----+-------+--------+--------------+

select Name 指定欄位

SELECT Name, Salary From Employee;

An unorder collection of a unquie object. No duplicate value.
不可以有重複的直，一般都是用在帳號上面。

Create set

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my_set= {1,2,3,4,5}
print(my_set)

output:

{1, 2, 3, 4, 5}

如果加重複會用最前面的

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my_set= {1,2,3,4,5,5}
print(my_set)

output:

{1, 2, 3, 4, 5}

adding set

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my_set= {1,2,3,4,5,5}
my_set.add(100)
my_set.add(2)
print(my_set)

output

‘{1, 2, 3, 4, 5, 100}`

今天想分享如何用 dictionary 字典方式存資料。

key and Value 如何使用宣槓取直

• collection of of {key:value} pairs
• no duplicate
• allow changeable and ordered

declare dictionary 宣告 dict

It's an unorder , it's not next to each other, so we can't use index like we use in list. Dictionary will have a a key and value look like this:

syntax:

declare: dictname= {key:value}
get key: print(dictname['key'])

Access and Get value 取我們的直:

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dict={
    'keyA':1,
    'keyB':2
}

取 key 的直: print(dict['keyA']) => 1
取所有直 print(dict) => {'keyA': 1, 'keyB': 2}

宣告不同 data type

Tuple is like list, but we can;t modify it, they are immutable. Tuple immutable 直，就是他的直不無法修改的，有些語法是用const類似這概念。

Create Tuple 建立tuple

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# Empty tuple
my_tuple = ()
print(my_tuple) #()

# Tuple having integers
my_tuple = (1, 2, 3) 
print(my_tuple) #(1,2,3)

# tuple with mixed datatypes
my_tuple = (1, "Hello", 3.4) 
print(my_tuple) #(1, "Hello", 3.4) 

# multiply value
x,y,z, *other = (1,2,3,4,5)
print(f"x: {x}, y:{y}, z:{z}, other:{other}")
#x: 1, y:2, z:3, other:[4, 5]

my_tuple = ("mouse", [8, 4, 6], (1, 2, 3))
print(my_tuple) #('mouse', [8, 4, 6], (1, 2, 3))

created without using parentheses

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my_tuple = 3, 4.6, "dog"
print(my_tuple)

# tuple unpacking is also possible
a, b, c = my_tuple

print(a)      # 3
print(b)      # 4.6
print(c)      # dog

my_tuple = ("hello")
print(type(my_tuple))  # <class 'str'>

# Creating a tuple having one element
my_tuple = ("hello",)
print(type(my_tuple))  # <class 'tuple'>

# Parentheses is optional
my_tuple = "hello",
print(type(my_tuple))  # <class 'tuple'>

Access Tuple Elements

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# Accessing tuple elements using indexing
my_tuple = ('p','e','r','m','i','t')

print(my_tuple[0])   # 'p' 
print(my_tuple[5])   # 't'

# nested tuple
n_tuple = ("mouse", [8, 4, 6], (1, 2, 3))

# nested index
print(n_tuple[0][3])  #'s'
print(n_tuple[1][1])  # 4

# Negative indexing for accessing tuple elements

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my_tuple = ('p', 'e', 'r', 'm', 'i', 't')

# Output: 't'
print(my_tuple[-1])
# elements beginning to 2nd
# Output: ('p', 'r')
print(my_tuple[:-7])

Slicing

python 有很多不同 function，因此我想在這篇寫所有 funtion 我會用到。我指的 function 不是傳 function，而是一些 libary function

Math

Datetime 時間

time

程式跑的時間

如果計算程式袍多就可以用這方法

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import time

# starting time
start = time.time()
# your code
for i in range(1,60):
    print(i)

#endtime
end = time.time()
runtime=end - start
print(" Runtime of the program is {runtime:%.8f}")
print(f"Runtime of the program is {runtime:.5f}")
#or
print(f"Runtime of the program is {(end - start):.5f}")

datetime

今天日期

• date.today 取今天日期

Pandas 筆記

今天我想分享我學的pandas筆記，我覺得對於分大數據很有幫助，他有點像mysql。請先下載module或package:pip install pandas`

Part1基本語法

連線CSV檔案

可以去github找相關csv檔案，然後去raw檔案做連線

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import pandas as pd
url = "https://raw.githubusercontent.com/mwaskom/seaborn-data/master/tips.csv"
tips = pd.read_csv(url)

print(tips)

pandas會回傳DataFrame格式。<class 'pandas.core.frame.DataFrame'>
下面是印出所有資料表內容。

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     total_bill   tip     sex smoker   day    time  size
0         16.99  1.01  Female     No   Sun  Dinner     2
1         10.34  1.66    Male     No   Sun  Dinner     3
2         21.01  3.50    Male     No   Sun  Dinner     3
3         23.68  3.31    Male     No   Sun  Dinner     2
4         24.59  3.61  Female     No   Sun  Dinner     4
..          ...   ...     ...    ...   ...     ...   ...
239       29.03  5.92    Male     No   Sat  Dinner     3
240       27.18  2.00  Female    Yes   Sat  Dinner     2
241       22.67  2.00    Male    Yes   Sat  Dinner     2
242       17.82  1.75    Male     No   Sat  Dinner     2
243       18.78  3.00  Female     No  Thur  Dinner     2

Head and Tail

• head(N): 是查前面N筆資料

  print(tips.head(10))

  output:

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  total_bill tip sex smoker day time size 0 16.99 1.01 Female No Sun Dinner 2 1 10.34 1.66 Male No Sun Dinner 3 2 21.01 3.50 Male No Sun Dinner 3 3 23.68 3.31 Male No Sun Dinner 2 4 24.59 3.61 Female No Sun Dinner 4 5 25.29 4.71 Male No Sun Dinner 4 6 8.77 2.00 Male No Sun Dinner 2 7 26.88 3.12 Male No Sun Dinner 4 8 15.04 1.96 Male No Sun Dinner 2 9 14.78 3.23 Male No Sun Dinner 2

• tail(N): 是查最後N筆資料

  print(tips.tail(10))

  output

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  total_bill tip sex smoker day time size 234 15.53 3.00 Male Yes Sat Dinner 2 235 10.07 1.25 Male No Sat Dinner 2 236 12.60 1.00 Male Yes Sat Dinner 2 237 32.83 1.17 Male Yes Sat Dinner 2 238 35.83 4.67 Female No Sat Dinner 3 239 29.03 5.92 Male No Sat Dinner 3 240 27.18 2.00 Female Yes Sat Dinner 2 241 22.67 2.00 Male Yes Sat Dinner 2 242 17.82 1.75 Male No Sat Dinner 2 243 18.78 3.00 Female No Thur Dinner 2

  Shape method

  shape 語法是用來查有多少欄與列

Create empty Excel File

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import openpyxl
fn = 'new_excel.xlsx'
wb = openpyxl.Workbook()
wb.save(fn)

Create Sheet工作表的

Create Empty Sheet 新增工作

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import openpyxl
fn = 'new_excel.xlsx'
wb = openpyxl.Workbook()
wb.create_sheet("Sheet1", 0) 
wb.create_sheet("Sheet2", 1)
wb.save(fn)

Read Excel Sheet 讀取excel檔案每個工作表的名稱

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import openpyxl
fn = 'new_excel.xlsx'
wb = openpyxl.load_workbook(fn)
print(wb.sheetnames)
print(wb.active)
print(wb.active.title)

output:

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['Sheet1', 'Sheet2', 'Sheet']
<Worksheet "Sheet1">
Sheet1

edit Name of worksheet 修改工作表名稱