Category Archives: Python
RMBS Prototype Model in Python
Posted by Shawn Zhang
on April 18, 2013
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Parameters
Parameters including : Total balance , Attach point, mortgage rate , Tranche Rate, Payment term and Prepayment CPR .
Cash Flow Chart result:
Full code(2 functions):
def rmbs_show(self):
self.clr_update_frame()
Label( self.update_frame, text="CPR" ).grid( row = 0, column= 0 )
w = Scale( self.update_frame, from_=0.01, to=0.20, resolution = 0.005, orient=HORIZONTAL, variable=self.rmbs_cpr, showvalue = True )
w.grid(row = Read more [...]
Conditional Checking in Python
Posted by Shawn Zhang
on March 22, 2013
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When story begins
In Python , there is a shortcut in conditional checking, I didn't take much care about the difference of below form of conditional syntax :
if var :
stmt;
if var is not None :
stmt;
if var != None:
stmt;
Explanation behind the scene is an analogy to difference of an empty string "" and NULL in a database . "" is an empty string but means something, NULL is nothing means nothing . In Python world , None equals NULL in Database , that's why "" == Read more [...]
Constraints on Arguments in Python
Posted by Shawn Zhang
on March 22, 2013
4 comments
When Dynamic Type comes to Trouble
As a dynamic programming languages , Python don't have a type on variables , as well as a arguments . This feature save us a lot workload and it enable us to focus on logical of program .
def add(x, y):
return x+y
print add(5,6)
>> 11
print add("D","E")
>> "DE"
print add(5.0, 6)
>> 11.0
Above function is straightforward and works fine if x and y are passed with int/ float/ string .
But things may Read more [...]
[译文]Decorators and Functional Python[draft]
Posted by Shawn Zhang
on January 16, 2013
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Original blog post wrote by Brian Holdefehr. This is a Chinese version of original post .
本文原文作者 Brian Holdefehr。若有不足，敬请斧正。
装饰器(Decorators) 是Python众多强大特性之一。装饰器除了本身编程语法上的作用之外，另外提供了一种有趣思维方式——"函数化"思维(a functional way)
我会从头开始介绍介绍装饰器的工作原理，接着会介绍几个必须了解的基本概念。之后，我们会详细深入探索一些装饰器实例以及其工作方式。最后我们会讨论一些装饰器的高阶应用，例如参数化装饰器(optional Read more [...]
Get Stock Quote Price API from Yahoo Finance via Python
Posted by Shawn Zhang
on December 28, 2012
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Difference against Google Finance / Sina.com
Yahoo provide more rich function regarding to the Stock API than Google / Sina.com does. particular ,it provide customize return format which customized by supply a parameter in calling URL . Full parameter specification pls refer to this link .(credit to Kelly Elias ) .
200 calls per second , you will be warned if you exceed this limits
csv file returned
No market depth as SIna.com provide
Provide stock indication such as " Earnings Read more [...]
Get Stock Quote from Goolge Web API via Python
Posted by Shawn Zhang
on December 27, 2012
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Background
Google has officially announce that it won't sustain ongoing of Finance API, but there still a available API via URL API . Return data from web server is xml format . We need to parse the return text in Python and extract data .
Get the Stock Data
Google Web API format ( http://www.google.com/ig/api?stock=C ) , this will request market data for security code "C" ( Citigroup :) ) xml return result:
<xml_api_reply version="1">
<finance module_id="0" Read more [...]
Get Security Quote of Chinese Market from Sina.com via Python
Posted by Shawn Zhang
on December 27, 2012
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Intro
Although articles have been written about calling security quote API of Sina.com . I'd like to take a dive into it via Python and try to setup a OO implementation. Sina.com API will offer 5-th market depth prices of Chinese Shanghai / Shenzhen Exchange Stock in real time style .
API structure
calling Sina.com Stock API can be straightforward , just type "http://hq.sinajs.cn/list=sh601012" in browser address . call back will shown as below ( click to enlarge ):
Cracking Read more [...]
Project Euler Problem 26
Posted by Shawn Zhang
on December 23, 2012
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Question
A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denominators 2 to 10 are given:
1/2
=
0.5
1/3
=
0.(3)
1/4
=
0.25
1/5
=
0.2
1/6
=
0.1(6)
1/7
=
0.(142857)
1/8
=
0.125
1/9
=
0.(1)
1/10
=
0.1
Where 0.1(6) means 0.166666..., and has a 1-digit recurring cycle. It can be seen that 1/7 has a 6-digit recurring cycle.
Find the value of d 
1000 for which 1/d contains Read more [...]
1000 for which 1/d contains Read more [...] Project Euler Question 14
Posted by Shawn Zhang
on December 20, 2012
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Question:
The following iterative sequence is defined for the set of positive integers:
n 
n/2 (n is even)
n 3n + 1 (n is odd)
Using the rule above and starting with 13, we generate the following sequence:
13 40 20 10 5 16 8 4 2 1
It can be seen that this sequence (starting at 13 and finishing Read more [...]
n/2 (n is even)
n 3n + 1 (n is odd)
Using the rule above and starting with 13, we generate the following sequence:
13 40 20 10 5 16 8 4 2 1
It can be seen that this sequence (starting at 13 and finishing Read more [...] Project Euler Question 29
Posted by Shawn Zhang
on December 19, 2012
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Question:
Consider all integer combinations of ab for 2 
a 5 and 2 b 5:
22=4, 23=8, 24=16, 25=32
32=9, 33=27, 34=81, 35=243
42=16, 43=64, 44=256, 45=1024
52=25, 53=125, 54=625, 55=3125
If they are then placed in numerical order, with any repeats removed, we get the following sequence of 15 distinct terms:
4, 8, 9, 16, 25, 27, 32, 64, 81, 125, 243, 256, 625, 1024, 3125
How many distinct terms are in the sequence generated by ab for 2 a 100 Read more [...]
a 5 and 2 b 5:
22=4, 23=8, 24=16, 25=32
32=9, 33=27, 34=81, 35=243
42=16, 43=64, 44=256, 45=1024
52=25, 53=125, 54=625, 55=3125
If they are then placed in numerical order, with any repeats removed, we get the following sequence of 15 distinct terms:
4, 8, 9, 16, 25, 27, 32, 64, 81, 125, 243, 256, 625, 1024, 3125
How many distinct terms are in the sequence generated by ab for 2 a 100 Read more [...]