Posts Tagged ‘resolution’

How to Avoid the 7 Most Frequent Mistakes in Python Programming

Monday, September 9th, 2019

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Python is very appealing for Rapid Application Development for many reasons, including high-level built in data structures, dynamic typing and binding, or to use as glue to connect different components. It’s simple and easy to learn but new Python developers can fall in the trap of missing certain subtleties.

Here are 7 common mistakes that are harder to catch but that even more experienced Python developers have fallen for.

 

1. The misuse of expressions as function argument defaults

Python allows developers to indicate optional function arguments by giving them default values. In most cases, this is a great feature of Python, but it can create some confusion when the default value is mutable. In fact, the common mistake is thinking that the optional argument is set to whatever default value you’ve set every time the function argument is presented without a value. It can seem a bit complicated, but the answer is that the default value for this function argument is only evaluated at the time you’ve defined the function, one time only.  

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2. Incorrect use of class variables

Python handles class variables internally as dictionaries and they will follow the Method Resolution Order (MRO). If an attribute is not found in one class it will be looked up in base classes so references to one part of the code are actually references to another part, and that can be quite difficult to handle well in Python. For class attributes, I recommend reading up on this aspect of Python independently to be able to handle them.

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3. Incorrect specifications of parameters for exception blocks

There is a common problem in Python when except statements are provided but they don’t take a list of the exceptions specified. The syntax except Exception is used to bind these exception blocks to optional parameters so that there can be further inspections. What happens, however, is that certain exceptions are then not being caught by the except statement, but the exception becomes bound to parameters. The way to get block exceptions in one except statement has to be done by specifying the first parameter as a tuple to contain all the exceptions that you want to catch.

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4. Failure to understand the scope rules

The scope resolution on Python is built on the LEGB rule as it’s commonly known, which means Local, Enclosing, Global, Built-in. Although at first glance this seems simple, there are some subtleties about the way it actually works in Python, which creates a more complex Python problem. If you make an assignment to a variable in a scope, Python will assume that variable is local to the scope and will shadow a variable that’s similarly named in other scopes. This is a particular problem especially when using lists.

 

5. Modifying lists during iterations over it

 

When a developer deletes an item from a list or array while iterating, they stumble upon a well known Python problem that’s easy to fall into. To address this, Python has incorporated many programming paradigms which can really simplify and streamline code when they’re used properly. Simple code is less likely to fall into the trap of deleting a list item while iterating over it. You can also use list comprehensions to avoid this problem.

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6. Name clash with Python standard library

 

Python has so many library modules which is a bonus of the language, but the problem is that you can inadvertently have a name clash between your module and a module in the standard library. The problem here is that you can accidentally import another library which will import the wrong version. To avoid this, it’s important to be aware of the names in the standard library modules and stay away from using them.

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7. Problems with binding variables in closures


Python has a late binding behavior which looks up the values of variables in closure only when the inner function is called. To address this, you may have to take advantage of default arguments to create anonymous functions that will give you the desired behavior – it’s either elegant or a hack depending on how you look at it, but it’s important to know.

 

 

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Python is very powerful and flexible and it’s a great language for developers, but it’s important to be familiar with the nuances of it to optimize it and avoid these errors.

Ellie Coverdale, a technical writer at Essay roo and UK Writings, is involved in tech research and projects to find new advances and share her insights. She shares what she has learned with her readers on the Boom Essays blog.

How to delete “Temporary Internet Files”/Content.IE5 with DEL and RD commands on Windows 7 / 8 folder contents – Clean Up Temporary files and folders to speed up and free disk space

Tuesday, February 3rd, 2015

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've been called urgently today by miss Jenia Pencheva who is the president of Christian Air Ticket Agency GoodFaithAir, her personal computer caused her quite a lot of headache, I've previously fixed it once and she was happy with that thus when she experienced problems she give me a call for remote IT support :).

She explahed her PC was unable to boot normally and in order to have some Windows she ended in Safe-Mode with Networking state. This problems caused her business losses as during PC in Safe mode the screen resolution even though with networking and she couldn't use the flight ticket ordering systems  to purchase her customers new tickets.  I've earlier installed TeamViewr on her PC so after Logging on the PC, I've immediately realized the Hard Disk was almost full (less than 1Giga free on C: Drive – where Windows install lived)

After a thorough investigation on which directory is occupying most of disk space (110GB) with a nice program called SpaceSniffer which is perfect for finding lost space on your hard disks, I've found System for ticket reservation Amadeus CRS (Computer Reservation System) was causing the disk full-full troubles.

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I've found troubling directory  was:

C:UsersgoodfaithairAppDataLocalMicrosoftWindowsTemporary Internet FilesContent.IE5

To solve it I first tried to Clean up Internet Explorer Cache (I've checked ticks Temporary Internet files, Cookies, History, Download History, Form Data, InPrivate Filtering Data).

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Then I used Microsoft Windows embedded clean manager (cleanmgr.exe) to run disk clean up, however Desk Clean Up managed to clear up only about 1Giga and on the computer HDD which is 150Gb still on Windows installation drive C: only 1.5GB were free.
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Besides that the system was having a second trouble as there were some failed updates (Computer was not shutdown properly but shutdown during Windows Update) and this was making the machine to enter Safe-Mode, I was fixing the system over TeamViewer session so after restart I had no way to see if Windows boots Normal or Safe-Mode after restart, thus to find out whether Windows was in Safe-Mode after another restart I've used below PowerShell one-liner script:

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PS C:> gwmi win32_computersystem | select BootupState

BootupState
———–
Fail-safe with network boot

Note that possible return results from above command are:

Normal boot
Fail-safe boot
Fail-safe with network boot

I've been struggling for a while (had to restart it multiple times) until finally I managed to make it boot in normal mode. Because PC was failing to apply some Windows Update, thus dropping by in Safe-Mode each time. To solve that I had to go and Delete two of the last Applied updates (KB2979xxxx files).
 

Control Panel ->  Program and Features -> View Installed Updates


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I've restarted and since I couldn't see the screen on Windows boot-time, I don't know what really happened but the PC booted again in Safe-Mode, and I thought the classical way to fix PC booting in Safe-Mode with SFC command will help:

C:> sfc /scannow

but for my surprise this helped not as the system continuously booted in Safe-Mode, to fix the Windows PC always booting to Safe-Mode, I had to change it running msconfig and unticking Safe Mode field

C:> msconfig

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Then I tried to delete Temporary Internet Files with below DEL cmd line
 

C:> del "C:UsersMyNameAppDataLocalMicrosoftWindowsTemporary Internet Files*.*"


To finally succeeding in manually delete huge Temporary Internet FilesContent.IE5 folder, I had to use good old RD (Remove Directory) command.

 

C:> RD "C:UsersusernameAppDataLocalMicrosoftWindowsTemporary Internet FilesContent.IE5" /Q /S

I used also following dels command to delete other common locations where Windows stores temporary files

For those who like to batch DeletingTemporary Internet Files and most common Temp locations to be cleaned on Windows boot I recommend you schedule a start of (clean-temporary-internet-files-content_ie5_folder.bat) on every PC boot.

To Clean-up other common Temporary file locations that could take you disk space the command line way run in new Administarator privileged command prompt:
 

cls
cleanmgr /sageset:99
del /F /S /Q "%systemroot%temp*.*"
del /F /S /Q "%systemroot%Prefetch*.*"
del /F /S /Q "C:Documents and SettingsDefault UserLocal SettingsTemporary Internet FilesContent.IE5*.*"
del /F /S /Q "C:Documents and SettingsDefault UserLocal SettingsTemp*.*"
del /F /S /Q "C:Documents and SettingsDefault UserLocal SettingsHistory*.*"
 
del /F /S /Q "C:Documents and Settings%UserName%Local SettingsTemporary Internet FilesContent.IE5*.*"
del /F /S /Q "C:Documents and Settings%UserName%Local SettingsTemp*.*"
del /F /S /Q "C:Documents and Settings%UserName%Local SettingsHistory*.*"
 
del /F /S /Q "C:Documents and Settings%UserName%Local SettingsApplication DataTemp*.*"
del /F /S /Q "C:Documents and Settings%UserName%Local SettingsApplication DataTemporary Internet FilesContent.IE5
*.*"
 
del /F /S /Q "C:AppDataLocalMicrosoftWindowsHistory*. *"
del /F /S /Q "C:AppDataLocalMicrosoftWindowsTemporary Internet FilesContent.IE5*.*"
del /F /S /Q "C:AppDataLocalMicrosoftWindowsTemporary Internet FilesLowContent.IE5*.*"
del /F /S /Q "C:AppDataLocalMicrosoftWindowsTemporary Internet FilesTemporary Internet FilesContent.IE5*.*"
del /F /S /Q "C:AppDataLocalMicrosoftWindowsTemporary Internet FilesTemporary Internet FilesLowContent.IE5*.*"
 
del /F /S /Q "C:Users%UserName%AppDataLocalTemp*.*"
del /F /S /Q "C:Temp*.*"
del /F /S /Q "C:Users%UserName%AppDataLocalMicrosoftW indo wsTemporary Internet FilesLowContent.IE5*.*
del /F /S /Q "C:Users%UserName%AppDataLocalMicrosoftW indo wsHistory*.*
 
 
::Rem: No need to duplicate the following section for each registered User
del /F /S /Q "%homepath%Cookies*.*"
del /F /S /Q "%homepath%recent*.*"
del /F /S /Q "%homepath%Local Settingscookies*.*"
 
del /F /S /Q "%homepath%Local SettingsHistory*.*"
del /F /S /Q "%homepath%Local SettingsTemp*.*"
del /F /S /Q "%homepath%Local SettingsTemporary Internet FilesContent.IE5*.*"
 
cleanmgr /sagerun:99

Note that in some cases running above commands might left you loose some sensitive data and in case where Internet is slow cleaning temporary files, might have impact on surfing also you will loose your history so be sure you know what you're doing as you might loose sensitive data.

Finally I've run MalwareBytes to clean up the PC slowness caused by Spyware and other left Malware I've run MalwareBytes, RogueKiller, AdwCleaner, RKill, TDSSKiller in order and I found and removed few Malwares as well.

That's all, hope you learned something new. Enjoy!
 

Reasons Why People Who Work with Computers seem to have a lot of spare time

Saturday, February 11th, 2012

Why people who work with computers have so much free time

While I was digging through some of my old data, I've found this funny caricature.
Here is the same picture in better 1178 x 975 pixels resolution
Enjoy 😉