Windows 10

08 Apr, 2017

I've come across some uncorroborated reports that some of the instructions, or examples, in Python for Kids don't work with Windows 10. Uncorroborated because it's unfortunately nothing more than "it don't work". Not spectacularly useful, so I've finally gotten around to installing Windows 10 in VirtualBox to test this out.

Instructions for Python installation remain pretty much the same, except that the latest version of Python is now 3.6, whereas on the last printing of PfK, it was 3.5. The results of installation aren't too dissimilar to Windows 7 either:

windows-10 start menu (small image)

I cherry-picked a few of the code samples at the beginning of the book to test, but wasn't expecting any of those to be a problem (they weren't), and then went through the more complicated code (turtle, tkinter) in the rest. Everything works as expected, except there is a little bit of graphical weirdness in the Bounce game (chapters 13, 14) where the ball seems to deform as it moves. I'm pretty certain this is an artifact of using Windows inside VirtualBox (I've never found animated graphics to work particularly well when you're in an OS inside an OS) - it's certainly not a problem in Linux or on a Mac. But interested to hear if anyone else has experienced the same issue on Windows:

Deformed ball


That's pants!

05 Apr, 2017

Lee writes:

I'm not fully understanding the HugeHairyPants program on pages 72-73 of Python For Kids. I initially thought that the loop would produce "huge huge hairy hairy pants pants," reasoning that the program would assign the first value to i, then the identical value to j, and continue the loop. So why is the variable j assigned all of the values? My thought was that the program commands i to be the first variable ('huge'), then stops there because the variable j is introduced next. Since there is no other variables after j, it then gets assigned every variable. Is this correct? (It doesn't sound right to me, though.)

So let's break the code down a bit more then. Here's the list...

hugehairypants = ['huge', 'hairy', 'pants']

...and then the first two lines of the loop code:

for i in hugehairypants:
    print(i)

If we run this code right now we get:

huge
hairy
pants

Each time the value in i is (effectively) replaced with the next value in the list (it's actually not quite as simple as that, but it can be easier to think of it that way when you start programming).

It's important to remember that every time we loop here, we're executing all the statements in the block of code - that's the indented part. And that's why if we look at the original example...

for i in hugehairypants:
    print(i)
    for j in hugehairypants:
        print(j)

...it first executes print(i), then it executes the second for-loop - that's looping over the hugehairypants list again, calling print(j) three times, then back to print(i) again, and so on. If we just look at the print statements Python is executing in these two loops, this is what it looks like:

print(i) # first for-loop - the value in i is now 'huge'
print(j) # second for-loop - the value in j is now 'huge'
print(j) # second for-loop - the value in j is now 'hairy'
print(j) # second for-loop - the value in j is now 'pants'
print(i) # first for-loop - the value in i is now 'hairy'
print(j) # second for-loop - the value in j is now 'huge'
print(j) # second for-loop - the value in j is now 'hairy'
print(j) # second for-loop - the value in j is now 'pants'
print(i) # first for-loop - the value in i is now 'pants'
print(j) # second for-loop - the value in j is now 'huge'
print(j) # second for-loop - the value in j is now 'hairy'
print(j) # second for-loop - the value in j is now 'pants'

If you need something more visual, I suggest drawing two rectangles on a piece of paper with 3 cells. Write the 3 values from the list in the cells (obviously it's not really two lists, but easier this way). Get two small coins; the first coin marks the value in i, the second coin marks the value in j. Work through the code as though you were running it yourself - move each coin to show how the value changes as we loop:

Visual guide


Epic Amazon Fail

22 Mar, 2017

Frankly this is bizarre, but if you're looking for Python for Kids, I suggest you don't buy on Amazon:

Expensive!! (small image)

Much as I'd like to be getting a cut of that price, I somehow doubt I'm getting anything -- and you're possibly getting a poor quality knock off, going by this:

https://twitter.com/billpollock/status/844030960333152256

(Some more discussion on Hacker News here: https://news.ycombinator.com/item?id=13924546)

Barnes and Noble looks to be a safer option - and you can still buy directly from No Starch Press of course.

Further update: Inc.com "Amazon's Tepid Response to Counterfeiters Frustrates Sellers"


askcolor

18 Jan, 2017

Isai writes:

I am having trouble with this code in page 176:

from tkinter import *
colorchooser.askcolor()

When I load it into IDLE, I get a blank canvas, and I can't close it, I have to restart the shell.

I have installed the proper ActiveTcl version (8.5), and no longer get the message giving me errors on startup.

When I run the previous code I was playing with (page 174), the canvas pops up and it all works again. Weirdly enough, the color picker pops up unprompted! I noticed that it does not bring up any buttons that appear in your book: [OK] [Cancel].

That's a bit of a gap in the book, because it doesn't make it clear that you need to create an instance of the top-level Tk widget first, before running that particular example (using tk = Tk()). So the first time you run this function: colorchooser.askcolor(), it's hanging, waiting for something that isn't there yet. Then you run the code on the previous page (which does create the Tk object), and that's when you suddenly get a popup dialog with the colorchooser in it.

So the code should really look like this:

from tkinter import *
tk = Tk()
tk.update()
colorchooser.askcolor()

When you run that, you should then get the colorchooser dialog immediately.

Update: One step I missed, is a call to tk.update(), which forces tk to update the screen. Once that's executed, the chooser will appear. The example is updated above.


Pro Alternatives

31 Dec, 2016

After something like 10 or more years completely ensconced in the Apple ecosystem, and now finding the price tag on the new MacBook Pros hard to justify, I'm looking around at alternatives. Before Apple, there was 7 - 8 (only occasionally fustrating) years of Linux in various flavours, so it makes sense to investigate linux-on-a-laptop options again. Looking at the Dell offerings though, it's clear they could learn from Apple's example -- at least in terms of pricing and consistency.

To start with, a higher spec'd MacBook Pro, from the US website:

Apple US (small image)

So that's £2,267 (at time of writing) for a 15" screen, i7 processor, 16GB of RAM and a 512GB solid state disk.

And for comparison, here's the same thing from the Apple UK and Apple NZ stores:

Apple UK (small image) Apple NZ (small image)

The NZ price is roughly £2,637. Apart from the fact that the US price is a few hundred pounds cheaper, they're roughly consistent (in both price, and what you get for your money). VAT (in the UK) and GST (in NZ) probably account for, at least part of, the price variation.

However, compare this with Dell's Precision series laptops. The Precision 15 5000 series (again with 15" screen, i7 processor and 512GB SSD) installed with Ubuntu Linux, comes in at a much more reasonable £1,483:

Dell US (small image)

The advantage of the Dell is that you can get a second 1TB HDD installed and the price is still less than the MacBook Pro (£1,558).

However, on the UK website, you can't order the additional hard drive, but the price is, at least, consistent (even if their website doesn't make it immediately obvious that you can order an i7 processor):

Dell - no HDD

Dell UK (small image)

However, compare with Dell NZ:

Dell NZ (small image)

That's £4,095, give or take a few pence. A price variation I can only see justified, if Dell haven't figured out international shipping, and are flying the laptop into the country in a business class seat. In addition, not only do the websites vary slightly in each country, but the configuration options vary as well. In the US you can get the additional HDD, in the UK and NZ you cannot (perhaps some different regulations applying to the ex-US models, and the additional HDD doesn't fit?). In the UK, you can get a single 1x16GB memory unit installed, in the US and NZ stores you cannot.

Conclusions? Apple: too expensive for a higher spec. Dell: either obscenely expensive, or inconsistent specifications, depending on which country I happen to be in (not to forget that if I want a bit of future proofing, it's difficult to be confident in the options). Other alternatives? A System76 Oryx Pro perhaps?

Update: Dell really is a bit of a mess. The NZ price for the XPS 15 (with ultra high def display) is only about £200 more than the UK price, but once again the configuration options look to be different between countries. Also with the XPS series, you don't have any option but to pay the Windows tax.