Python 3 Not Backwards Compatible with Python 2

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Understanding why the example program would not run in Python 3 and how to fix it.

Khan Academy

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It's not only the print() and input(). If I remember correctly, simply making a function return was a statement before, now it is a function (like print "something" is now print("something")). Furthermire, the i/o-stuff has changed. I don't know if there are other important differences, but these round up the given examples in the video.

Permafrostrock

Moaaaar! These are AWESOME. I can't wait for you to cover some deeper topics, but these are brilliant. Thanks!

bearchildofdeath

Instead of doing eval(input("Enter a non-negative integer to take the factorial of: ")), you can do int(input("Enter a non-negative integer to take the factorial of: ")) for Python 3. FYI :-).

thebestbestman

Programming tutorials from Khan! Excellent! May I suggest doing solutions for project euler?

computerex

omg i never knew u did programming stuff on Khan Academy! This is AWESOME!

camelCaseFTW

Also:
number = int(raw_input("enter a positive integer: "))

works fine :D

computerex

You maybe want to introduce viewers to the concept of types (the type() function in Python will return the type of variable). raw_input() in Python 2 returns a string. input() in Python 2 expects Python syntactically correct input and returns the input evaluated with the correct type (so you could enter '[1, 2, 3]' and it would evaluate this to an actual list).

parkamark

@944Nima By that I mean a language such as java or c++ where in my opinion the object oriented aspect is much more pronounced and is much more applicable to developing large pieces of software by using large complex objects and classes. Python doesn't hold a candle to the major object oriented languages it is primarily a scripting language.

slsl

@944Nima I'm curious about what features you are referring to as C++ has a very rich set of features when it comes to OOP.. When they designed Java they actually chose to skip some of those features like multiple inheritance.

kacklal

What do you use for drawing on the screen? I'm interested in the hardware & software.

I'm looking forward to watching all the Python videos you produce, I just found out about Kahn Academy, thanks so much!

zbuffered

I get a 'run in parallel' error no matter what I try to do regarding this first line of code

sedenions

Any chance of later doing videos in more object oriented languages?

slsl

In general using eval() on a user input is a really bad idea. The user can input any code, say something to delete the contents of your hard drive, and your program would run it.

PeterCollingridge

@angeldown Why is it even like this though? Why are their different commands for certain variables. I know in Basic and C++, you would delcare a variable and then use the same input type to put whatever you needed into it.

ForeverWiked