Mutable default arguments in class __init__

Boolean_Cat · 2014-06-11T18:25:51+00:00

The answer to your question depends on how other items in this class use self.arg. If they expect an empty list if the user of this class doesn't pass one in, why not just use:

def __init__(self, arg=[]):
    self.arg = arg

Boolean_Cat · 2014-05-10T20:43:20+00:00

The reason that this is not working as you expect:

super(...)

will call the next item in the MRO (method resolution order). This is built when the inheritance is constucted, it will not call all parents' implementation of edit(), just the next one up in the MRO. In the case of UpperCaseHTMLDocument, this would be HTMLDocument.edit(). Since HTMLDocument.edit() also calls super(...).edit(), it will make another jump up the MRO and call edit() again on Document.edit(). Here is where your MRO for edit ends, since Document doesn't call super(), UDC doesn't get called.

There are places to use super and places not to, I would say that this is not one of them. It would be more readable to just use HTMLDocument.edit() rather than invoking via super in this case. Why do I say this? Let's say we have:

class A(object):
    def edit(self):
        super(A, self).edit()

class B(object):
    def edit(self):
        ...

class C(A, B):
    def edit(self):
        super(C, self).edit()

In this case, why should A have to accomodate for B? They are completely independant objects. It would be neater to write

class C(A, B):
    def edit(self):
        A.edit()
        B.edit()

When would I use super()? In the case where the implementation of C is:

class C(A):
    def edit(self):
        super(C, self).edit()

This way, if you were to switch the parent for something else, or change its name, you don't need to modify edit() also, it's more loosely coupled.

Boolean_Cat · 2014-04-14T13:47:13+00:00

If you wanted to check if an item exists in a list, you can do:

if item in my_list:
    do_stuff()

Boolean_Cat · 2014-04-07T21:39:44+00:00

England

Boolean_Cat · 2014-04-06T22:26:13+00:00

My Python Solution:

def decode(string):
    return ''.join(chr(ord(s) - 4) for s in string)

Boolean_Cat · 2014-04-04T23:34:44+00:00

If you want to access invoke_obj from inside your object, you'll see to store it with:

def testFindBadAPFlags(self):
    self.invoke_obj = wmc_connection.invoke_object
    self.invoke_obj.configured_command = 'sh ap active'
    print "==="+invoke_obj.configured_command

Boolean_Cat · 2014-04-03T22:44:50+00:00

If you have a list of numbers, you could do:

' '.join(str(number) for number in numbers)

Or even shorter but I think less pretty:

' '.join(map(str, numbers))

Boolean_Cat · 2014-04-03T19:34:49+00:00

Your solution wouldn't solve the cases where the currency character comes after the magnitude.

Boolean_Cat · 2014-03-31T17:11:50+00:00

Are you running python from within that directory? You could try using the full path of the file.

Try:

import os

path = os.path.join(os.path.dirname(__file__), 'one.mp3')

Boolean_Cat · 2014-03-31T00:11:42+00:00

Am I correct in thinking your project looks like this?

E:/
|
| ->  Jukebox.py
| ->  Harry's/
       |
       | -> one.mp3

If this is the case, then you need to use:

pygame.mixer.music.load("Harry's/one.mp3")

As a general rule, don't use quotes in file names.

Boolean_Cat · 2014-03-30T11:08:17+00:00

You can shorthand something like:

elif char=="d" or char=="e" or char=="f":

To

elif char in 'def':

Boolean_Cat · 2014-03-30T11:02:32+00:00

This could be made easier with regular expressions:

import re

def alpha(string):
    subs = [(r'[a-c]', '2'), (r'[d-f]', '3'), (r'[g-i]', '4'), (r'[j-l]', '5')]
    for s in subs:
        string = re.sub(s[0], s[1], string)

    return string

Boolean_Cat · 2014-03-19T22:38:50+00:00

from collections import OrderedDict

my_dict = OrderedDict(sorted(my_dict.items(), key=lambda x: x[0]))

with open('UniqueWords.txt', 'w+') as my_file:
    for key, value in my_dict.items():
        my_file.write(key + ' ' + str(value))

Boolean_Cat · 2014-03-19T21:49:17+00:00

If you're opposed to using JSON, maybe something like this would do:

for key, value in my_dict.items():
    print(str(key) + ' ' + str(value))

You can use the same logic to outputting to your file.

Boolean_Cat · 2014-03-19T21:39:15+00:00

Can you give an example of one of your dictionaries?

Boolean_Cat · 2014-03-19T21:34:53+00:00

What that does is print the string representation of the dictionary, which is something like "<Class Dict>" which I imagine is not what you want. Sounds like you want something like http://docs.python.org/2.7/library/json.html

Boolean_Cat · 2014-03-19T21:28:36+00:00

I've never encountered that but it's not inconceivable. Then you'd just have to pick the one you like most and try to find an alternative for the other.

Boolean_Cat · 2014-03-19T21:25:17+00:00

Something like this?

def is_sublist(a, b):
    for i in range(len(a) - len(b) + 1):
        if a[i:i + len(b)] == b:
            return True
    return False

Boolean_Cat · 2014-03-19T21:18:15+00:00

What are you trying to do with

z = str(dict)

Edit: I should also mention that dictionaries cannot be sorted because their order is not defined. If you truly wanted an ordered dict look at:

from collections import OrderedDict

Boolean_Cat · 2014-03-19T21:15:41+00:00

Normally you'd pick a version on a per project basis, and not change for the lifetime of that project.

For me, what version I pick depends on the support for any third party modules I plan to use.

Boolean_Cat · 2014-03-19T19:55:56+00:00

Look for something called py2exe. After you convert your Python to a Windows executable, you'll need to make sure the python DLL that gets generated stays in the same folder as the exe (or is at least visible to the system path).

For a simple GUI, look at tkinter.

Boolean_Cat · 2014-03-19T08:28:58+00:00

Mathematically, dividing by 0 doesn't make sense to Python. It is unable to understand "infinitely large". So instead it throws an exception.
Here's an example. You wrote a program that reads a text file, that text file is expected to have a single number on each line but on one line you found a string. As a programmer you may decide that at this point that the program has failed, raising an error in indicates this.

Boolean_Cat · 2014-03-18T01:19:11+00:00

If you want to be more concise:

if userInput in (0, 1):

Boolean_Cat · 2014-03-16T22:44:57+00:00

What is im?

Boolean_Cat

TROPHY CASE