Python List Comprehension

  List Comprehension沒有統一譯名(數學推論出的式子)

#列表推導式

# 列表高效率單行建構
arr1 = [i for i in range(10)]

# 列表內元素限制產生
arr2 = [x for x in arr1 if x % 2 == 0]

# 列表內元素多重限制產生
arr3 = [x for x in arr1 if x >= 3 and x % 2]

# 巢狀列表元素產生
arr4 = [(x, y) for x in range(3) for y in range(4)]

print(arr1)
print(arr2)
print(arr3)
print(arr4)

SQL 一次insert 多筆

 -- 傳統

 insert into test.customer(pin,first_name,last_name) values(601,"Bush","Kim");

 insert into test.customer(pin,first_name,last_name) values(602,"Grace","Kun");

 insert into test.customer(pin,first_name,last_name) values(603,"Jully","LAin");

-- oracle 

insert all 

into test.customer(pin,first_name,last_name) values(601,"Bush","Kim")

into test.customer(pin,first_name,last_name) values(602,"Grace","Kun")

into test.customer(pin,first_name,last_name) values(603,"Jully","LAin");

-- mysql

insert into customer(pin,first_name,last_name) 

values(601,"Bush","Kim"),

(602,"Grace","Kun"),

(603,"Jully","LAin");

 Python 的日期字串格式摘要:

Python's strftime directives

Code	Meaning	Example
%a	Weekday as locale’s abbreviated name.	Mon
%A	Weekday as locale’s full name.	Monday
%w	Weekday as a decimal number, where 0 is Sunday and 6 is Saturday.	1
%d	Day of the month as a zero-padded decimal number.	30
%-d	Day of the month as a decimal number. (Platform specific)	30
%b	Month as locale’s abbreviated name.	Sep
%B	Month as locale’s full name.	September
%m	Month as a zero-padded decimal number.	09
%-m	Month as a decimal number. (Platform specific)	9
%y	Year without century as a zero-padded decimal number.	13
%Y	Year with century as a decimal number.	2013
%H	Hour (24-hour clock) as a zero-padded decimal number.	07
%-H	Hour (24-hour clock) as a decimal number. (Platform specific)	7
%I	Hour (12-hour clock) as a zero-padded decimal number.	07
%-I	Hour (12-hour clock) as a decimal number. (Platform specific)	7
%p	Locale’s equivalent of either AM or PM.	AM
%M	Minute as a zero-padded decimal number.	06
%-M	Minute as a decimal number. (Platform specific)	6
%S	Second as a zero-padded decimal number.	05
%-S	Second as a decimal number. (Platform specific)	5
%f	Microsecond as a decimal number, zero-padded on the left.	000000
%z	UTC offset in the form +HHMM or -HHMM (empty string if the the object is naive).
%Z	Time zone name (empty string if the object is naive).
%j	Day of the year as a zero-padded decimal number.	273
%-j	Day of the year as a decimal number. (Platform specific)	273
%U	Week number of the year (Sunday as the first day of the week) as a zero padded decimal number. All days in a new year preceding the first Sunday are considered to be in week 0.	39
%W	Week number of the year (Monday as the first day of the week) as a decimal number. All days in a new year preceding the first Monday are considered to be in week 0.	39
%c	Locale’s appropriate date and time representation.	Mon Sep 30 07:06:05 2013
%x	Locale’s appropriate date representation.	09/30/13
%X	Locale’s appropriate time representation.	07:06:05
%%	A literal '%' character.	%

Python令人混淆的底線命名

 _name:

class 中的成員變數的變數名稱前有一底線,代表預計標示為是class內部用(非強制性)

module內定義的方法名稱前有一底線,代表不公開,需使用FQN可使用
      也可改寫__all__()表示出外界使用
      還有如果直接讓module於python的shell執行也會顯示使用

name_:變數名稱後有一底線,只是為解決關鍵字衝突

_ _name:

class 中的成員變數的變數名稱前有二底線,代表會在前加上一底線及一class名稱改寫,呈現給外部使用
      但class內部使用依舊使用無改寫原名稱


反向植入成員變數,如命名規則一底線及一class名稱再加二底線的變數名,例"_ClassName_ _VarName"
後來出現這Class名稱的class定義,雖內部無此變數,但會自動加入
_ConfuseClass__confuseVar1=45
   
class ConfuseClass:
    def testFun(self):
         return __confuseVar1

ConfuseClass().testFun()

_ _name_ _:
   代表python內class的特殊成員(不好的用法)如__init__()

_ :在python command shell 中代表最後一個物件,可能是一個值或list等