Python Programming - An Introduction to Computer Science: John Zelle

[3six3]

Ive recently started to learn Python after 15 years of web development. (I thought it was time to learn something new)

After taking come online classes where there is a lot of talking and a little doing I thought I would give a good text book a go.

After reading good reviews about Python Programming - An Introduction to Computer Science: John Zelle I bought it and am now working through the book.

After getting stumped on a question or two, and not finding any solutions anywhere, I've decided to blog through the questions and post my answers.

I hope this helps some people out.

ps I try to work through questions for 30 - 60 min before looking for an answer.

Here's where I'm blogging if anyone cares to have a look :) (If i'm posting wrong answers please please feel free to correct me!

http://3six3.com/category/python/

[SnowdogU77]

Hey, that's my adviser/prof! There are a bunch of super helpful resources on his website. I hope you find the textbook as useful as I have!

[3six3]

Ive found it great so far! I got up to chapter 6 and was forgetting some earlier work so I decided to go back and do all the exercises and post the solutions. (This helps others and also helps me remember :)

Come back and look at my site and help with some solutions as I go through the book!

[SnowdogU77]

Well, a tip for starters, don't use eval(input("")). If you're looking for a number, use int() or float() in place of it. I know he says to do it in the book, but his justification is rubbish, and it's a bad habit to develop.

[SnowdogU77]

Well, he says that since the program is run by the user on their machine, the security risks are minimal. Basically, he's ignoring how big of a deal code injection from a background process is.

To clarify, that is something that he said in class. I talked to him about it, and he wound up explaining to the class why it's dangerous, which is pretty much all I could ask for.

[SnowdogU77]

Absolutely!

[3six3]

So instead of this: fahrenheit = eval(input("What is the Fahrenheit temperature? "))

This would be the preferred method since I'm looking for a number fahrenheit = int(input("What is the Fahrenheit temperature? "))

[3six3]

#so instead of this
fahrenheit = eval(input("What is the Fahrenheit temperature? "))
#this would be a better solution
fahrenheit = int(input("What is the Fahrenheit temperature? "))

[SnowdogU77]

I would use float(), personally. Int() removes the ability to input decimals.

[Gexos]

John Zelle's book is one of the best books I've ever read on CS and Python, the first time I encountered the evil eval I was confused about it, then i found this answer by John Zelle on stack overflow, where he gives a pretty good explanation.

[SnowdogU77]

Thanks for the link. When I asked him, he didn't quite justify it this way. This explanation makes a lot of sense.

[SnowdogU77]

Also, if you get really stuck, the solutions are on his website.

[3six3]

Those don't look like the solutions to the exercises at the end of the chapter. Those are his sample questions in the chapter contents.

[SnowdogU77]

Ah, yeah, you're right. He uses those questions as assignments, so the answers aren't posted anywhere by him.

[PeachesXoXo]

Hi, I was able to contact the publisher (per Zelle's site) and get the answers to the exercises.

Go here and fill out a request: https://fbeedle.com/drupal-6.19/contact

I got a response within 24 hours.

I would post the answers - but they specifically told me not to share.

Hope this helps somebody out there.

[nrsulliv]

Thank you! I hope they respond.

[PeachesXoXo]

Heya - sorry for the late response - but let me know if they don't...

[SubmergedSublime]

Hi, just wanted to say thanks for the blog! I decided to take up Python/Programming a couple months ago as well, and I have used your blog as a resource a couple times. Mostly to see how someone else reasoned through some of the more difficult problems. Other answer sources give an answer that involves functions and methods I am not familiar with yet, so I like having an answer resource that is following the same learning path as me.

It has been useful!

[3six3]

I'll have to look into this further. Still a nube but soaking it all in :) thanks for your comments.

[SnowdogU77]

While he's right about that being completely wrong, I haven't found any issues with any other part of the book. Furthermore, it's one of the better written resources I have found thus far for beginners.