Mainly Tech projects on Python and Electronic Design Automation.

Sunday, November 02, 2008

Comments on a "Python Tutorial"

I thought I'd go through your tutorial on Python and make some notes if thats OK.

"No ++ / --":

I think this was the same kind of decision as Python not allowing assignments in if conditionals. There is a a high instance of problems caused by confusion over the misuse of increment/decrement operators in languages like C. They can make it harder to read a program.

"Slow in comparison to compiled languages" - (Here comes the dynamic language supporters usual reply): Yes, but often getting something right is much more important and often never requires the speep that Python gives you. People have prototyped in Python and shipped the prototype as it fits all quality metrics in a far shorter development time. I recently had a case of that myself here.

"Whitespace for indentation": Arguably a positive feature. It should read "whitespace for block delineation" or something. Run a pretty printer on say a C source file and it will try and indent it so that the visible level of indentation mirrors the logical structure of the code. Code is hard to read if the indentation does not follow the logic. Python recognises this and goes further in saying that the common use of block start and end delimeters such as {/} or begin/end are superfluous and only help in writing misleading code.

You seem to have missed the importance of docstrings in Python.

range "(good for indexing)": True, but in idiomatic Python you are much more likely to iterate over the members of a collection object rather than create an index using range:

for x in my_list:

rather than:

for i in range(len(my_list)):

....x = my_list[i]

"Functions work in python much like they do any other language": those with only Java and C experience might miss out on the extended argument passing of Python functions if not made aware.

"Classes are more basic than what you will be use to from java": In what way? There maybe less to learn to become equally proficient but I see this as a good thing. Note that Python is dynamic, meaning that, if you wanted to, you can modify classes and instances at run-time. Its not necessarily a X language does classes better than Y. Python does things differently and if you try and constrain Python to how you use OO in Java, you won't get the best from it.

"from os import *": It's a bad Python habit. You want to warn students off this, as maintenance can suffer.

"We can raise our own exceptions": It could be but shouldn't be a string. best to use an exception type.

"Numbers": There are decimals too, which are good for financial calculations.

"Tuples": If each position in a sequence has explicit meaning then you should use a tuple, e.g. a point on a surface might be the tuple (x,y). coordinates of a car would more likely be a list of points.

"Strings": Misses triple quoted strings.

Filter and map, although present, have declined in use due to the later addition of the powerful list comprehension and generator comprehension features.

One-liners in Python: Difficult to do. Usually people write multi-line scripts in an editor. In a shell such as bash which has multi-line string delimeters you might be able to use a multi-line single quote for bash and embed a multi-line python program using Pythons -c argument and restricting your Python to double quotes if needed.

Have fun with Python.

- Paddy.

Paddy3118 said...


My notes are longer than your blog entry :-)

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