473,746 Members | 2,701 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

Enjoying Inheritance and operator Overloading

I've been programming in python for a few months now - and returning
to programming after a gap of about ten years I've really enjoyed
learning python.

I've just made my first forays into inheritance and operator
overloading (both concepts that I initially found hard to grasp).

I've written a simple config file parser - and I thought I'd
experiment with making the interface easier by subclassing dict and
overloading the __setitem__, __getitem__ and __delitem__ methods......

The thing is I'm not 100% certain that what I've done is good python -
or even valid python.

As an example (my config parser is a bit more complex) I've shown my
technique for creating a 'case insensitive' dictionary... and would
welcome comments.

class lowerDict(dict) :
"""A case insensitve dictionary. It converts the key to lowercase
when
'getting', 'setting' or 'deleting' an item.
May not work with pop or other methods."""
def __init__(self):
dict.__init__(s elf)

def __setitem__(sel f, item, value): # setting a
keyword
item = item.lower()
dict.__setitem_ _(self, item, value)

def __getitem__(sel f, item):
"""To implement lowercase keys."""
key = item.lower()
return dict.__getitem_ _(self, key)

def __delitem__(sel f, item): # deleting a keyword
key = item.lower()
if not self.has_key(ke y):
raise KeyError(item)
dict.__delitem_ _(key)
if __name__ == '__main__':
a = lowerDict()
a['HELLO'] =3
print a
Jul 18 '05 #1
1 2037
>
def __delitem__(sel f, item): # deleting a keyword
key = item.lower()
if not self.has_key(ke y):
raise KeyError(item)
dict.__delitem_ _(key)
Oops - except dict.__delitem_ _ ought have both self and item as arguments....

Regards,
Fuzzy

http://www.voidspace.org.uk/atlantib...thonutils.html


if __name__ == '__main__':
a = lowerDict()
a['HELLO'] =3
print a

Jul 18 '05 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

2
4586
by: cppsks | last post by:
Here is the code that I am working with: #include <new> #include <iostream> #include "stdlib.h" class Base1 { public: Base1() { cout << "Base1:" << this << endl; }
0
1439
by: cppsks | last post by:
Hello. I posted a question regarding this yesterday. I came up with the following solution but I am a little hesistant as to this solution having any side-effects that I am not aware of. The solution seems to work though. Please let me know if this is okay or if I need to modify something here. Thanks !!!! Here is what I have: #include <new> #include <iostream>
6
1790
by: woosu | last post by:
Hello ladies and gentlemen. I have a relatively simple problem that I've been unable to solve. In the interest of learning C++, I've decided to write a simple game. The basis for the game is 8x8 board (think chess). I decided to implement iterators so it'd be easy to analyze the board position etc. Basically I have the following hierachy:
6
3283
by: apm | last post by:
Recently I have had to use a value type for a complex structure because I don't know how to override the = operator. Can the operator ever be overloaded? Or can inheritance be used with value types?
6
2851
by: Massimo Soricetti | last post by:
Hello, recently I wrote a little class which has to wrap two different type of data, showing the same external interface. I used operator overloading, but the same result I could eventually obtain with two classes derived from an abstract base class containing only the interface functions. So, when it's worth to use overloading mechanism instead of abstract/inherited?
2
7396
by: Tom Smith | last post by:
I'm having difficulty with overloading ==, and it's making my brain melt - can you help...? What I want to have is: 1) A base class A with virtual operator== defined (no problem) 2) A class B derived from A with operator== overridden (again, no problem) 3) Pointers A* b1, b2 which may actually point to instances of B, where I can call (*b1)==(*b2) and have it use the overridden form of == found in B. Having written this all out I'm...
0
2052
by: erik.erikson | last post by:
I am getting a compiler error that I can't well explain or even understand the origin of (though I boiled it down close...). Below is a bare-bones example. What I am doing is defining the increment operator in a class and then defining a derived class and using the derived class. When I try to use the increment operator on an instance of the derived class (as an instance of the derived class, not when used as an instance of the base...
8
1391
by: Matthias Pfeifer | last post by:
Hi there, i am implementing a Point and Vector class and found that they have some things in common. Therefore i introduced a common parent class called ndimobj, that hosts an array of n values, offers some constructors and the following operator template<size_t n, typename T> class ndimobj {
3
3894
by: puzzlecracker | last post by:
Are static method inheritable under csharp rules, if so how can they be used? Can they be virtual? They reason I am asking is because operators are static, and I don't understand how can we apply operators to base and derive classes simultaneously?
0
8800
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
0
9349
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
1
9285
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
0
9218
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
1
6772
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupr who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
0
4575
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
0
4836
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
1
3292
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
3
2199
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.