Re: Beginning Python Tutorial (Part 2)

crystalattice · #1 30-Jul-2005, 22:27

I just posted a GID Community blog entitled: Beginning Python Tutorial (Part 2).

Quote:

Last time I covered the basics of running Python programs. Today I'll talk about the types and operators used in Python, as well as the syntax Python uses.

Python is based on the C programming language and is written in C, so much of the format Python uses will be familiar to C and C programmers. However, it makes life a little easier because it's not made to be a low-level language (it's difficult to interact heavily with hardware or perform memory allocation) and it has built-in "garbage collection" (it tracks references to objects and automatically removes objects from memory when they are no longer referenced), which allows the programmer to worry more about how the program will work rather than dealing with the computer. read more...

Please let me know what you think.

This is an auto-generated message posted by GIDNetwork™ on behalf of the author.

JdS · #2 31-Jul-2005, 10:07

Again, a really interesting article. Thank you.

I was wondering, what about block / multiline comments? Does it exist for Python? Comments start with #, right? In the article, you mentioned "asterisk", was that a typo?

And I am not quite clear about the indentation bit under Python Syntax. I think it would help me understand if you can supply a if/else example below in a reply. What about else ifs?

crystalattice · #3 31-Jul-2005, 12:25

Quote:

Originally Posted by JdS

Again, a really interesting article. Thank you.

I was wondering, what about block / multiline comments? Does it exist for Python? Comments start with #, right? In the article, you mentioned "asterisk", was that a typo?

And I am not quite clear about the indentation bit under Python Syntax. I think it would help me understand if you can supply a if/else example below in a reply. What about else ifs?

Yes, I made a boo-boo. It is indeed the "pound sign" or "hash mark" that is used to make comments, not the asterisk. (I was looking at the number 8 key while typing

). And I haven't read anything so far that says Python does multi-line comments. I'm guessing that you just add a hash prior to every line of comment.

Here's an if statement borrowed from the Python.org tutorial:

Code:

>>> x = int(raw_input("Please enter an integer: "))
>>> if x < 0:
...      x = 0
...      print 'Negative changed to zero'
... elif x == 0:
...      print 'Zero'
... elif x == 1:
...      print 'Single'
... else:
...      print 'More'
...

I should mention that I was wrong when I said the "..." don't appear in the Python interactive prompt. It does appear when writing indented code blocks, such as if statements. However other times it doesn't appear, so don't sweat it too much.

I was going to cover "else if" when I talk about control loops, but as you can see, "else if" is shortened to "elif". You can use a final "else" at the end of the code block, if needed.

The amount of indentation doesn't matter, only how the indentation relates to other indented statements. The easiest way to explain it is with the "if, else" statement.

CPP / C++ / C Code:

/*  Warning:  bogus C code!  */

if (some condition)
        if (another condition)
                do_something(fancy);
else
        this_sucks(badluck);

In C/C++, this would be not do what the programmer intended, since C/C++ "else" statements only relate to the closest "if". However, since indentation is significant, the intention of the writer is clear: the "else" statement applies to the first "if" and not the closest one.

If this doesn't clear things up, please let me know.

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Re: Beginning Python Tutorial (Part 2)

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