This course will continue the introduction to Python programming that started with Python Programming Essentials. We'll learn about different data representations, including strings, lists, and tuples, that form the core of all Python programs. We will also teach you how to access files, which will allow you to store and retrieve data within your programs. These concepts and skills will help you to manipulate data and write more complex Python programs. By the end of the course, you will be able to write Python programs that can manipulate data stored in files. This will extend your Python programming expertise, enabling you to write a wide range of scripts using Python This course uses Python 3. While most Python programs continue to use Python 2, Python 3 is the future of the Python programming language. This course introduces basic desktop Python development environments, allowing you to run Python programs directly on your computer. This choice enables a smooth transition from online development environments.
Answering Common Python Questions
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Do curso por Rice University
Python Data Representations
316 classificações
Na lição
Strings
This module will teach you about Python's string data type and its capabilities. Strings are used to represent text within programs.
Conheça os instrutores
Scott RixnerProfessor
Computer Science
Joe WarrenProfessor
Computer Science
[MUSIC]
Welcome to class.
In a previous lecture, we looked at how to gather information about Python
from various resources on the web.
In particular we looked at the documentation at python.org, and
we briefly looked at the CodeSkulptor docs.
In this lecture, I'm going to talk about another valuable resource on the web
that's very helpful in answering common questions that you encounter when you're
learning how to script in Python.
Let's get to it.
As your knowledge of Python scripting increases,
you're going to find that there's always going to be questions that you're going to
have that you don't know the answer to immediately.
Part of our goal in this specialization is to kind of teach you the answers to kind
of the common questions, but we can't cover everything.
So what you're going to see as a beginning or even an expert coder, you're going to
be searching the web for answers to your common programming questions.
So as I mentioned in the intro, we already have some places to start,
things like the docs on python.org, or the CodeSkulptor docs.
But really, the right way to approach this is to use Google or
a web engine to go out and search for the answers to your questions.
So, let's go through and actually do one to get started.
So I'm going to say, let's see, what would be a good question?
We're working on strings right now.
How can we convert a string into all uppercase,
so how can I convert a string
into uppercase in python?
All right, and Google very helpfully came back with a bunch of results here,
let's go with the first one here.
And so I'm going to go out and pop it up here, and
it says how to change a string into uppercase.
And it looks like the question says, he's got some code here and
he said this gave an error message, and we can go down and read the answer.
And it says okay, this answer said, use the upper method, kay.
Hm, okay, let's try the upper method, so
we kind of found a potential solution here.
Let's go out and write some code that tries that,
so let's call it my_string= Hello World, and
I'm going to print (my_string.upper), and
I run that and yay, it converted hello world into uppercase.
So this is kind of a canonical example of how you might use web search
to answer a common question that comes up when you're working with Python.
Okay, let's do another example of searching for
some information related to Python on the web.
So one of the main differences between Python 2 and Python 3 is that in Python 3,
you have to put parentheses around the arguments to print.
So let's see if we can find out some more information about that.
So maybe let's formulate a question,
so why does Python 3 require
parentheses around print?
So we get some more results here, and I don't know,
let's look at this second one here, why is parenthesis voluntary in Python 2.7?
So again, we've got a response here, it says why is parenthesis voluntary.
If you read the question it says well, in Python 2 we can say print,
open parenthesis, Hello, world, and it prints out Hello, world.
We can also say print with no parenthesis around it and we get hello, world.
However, if we do this in Python 2, we come back
out with parenthesis around Hello world, in this case we just get Hello world.
And so we can kind of read down to some of the answers to the question here, and
the first one says something interesting.
It says in Python 2, print is actually a statement and not a function, so
that's probably one of the most important things in Python 2, print's a statement,
so we don't need parentheses.
In Python 3, it's a function so we do need parentheses.
It still didn't really answer that first question up there in terms of
why is this behavior the way it is?
We could go down here it says,
it has some interesting side effects here and we have well,
looks like a very complicated answer here that I don't even parse that well.
Let's look at the third one down here it says, let's see, basically Python 3,
apparently it was a special statement to print all the strings of arguments, so
it's very interesting here.
It says that the grammar is ambiguous, so what that means is when you go up here and
you say something like print parenthesis around Hello world.
The way that a parenthesis around an expression is interpreted is that it
just evaluates the expression inside, except if it's a tuple.
If it's a tuple, where there's basically things separated by commas,
then it actually retains the parenthesis, so
that's really the thing that gave rise to these two different examples here.
And we know this question is not that critical, but
the thing I want to point you to here is that this site that we just looked at
here was the same site that we looked at the last one.
And the same site that dominated the search results for
both of these questions.
And that's Stack Overflow, so
let's take a little bit of a longer look at Stack Overflow next.
Okay, let's talk a little bit about Stack Overflow.
So as you saw, when we pose a programming question to Google,
many of the search results point to Stack Overflow.
So Stack Overflow is a question and answer website for
both beginning and expert programmers.
Its importance can't really be understated.
In fact, I hear people sometimes joke when we say the following.
That essentially the key to programming is just being able to reduce whatever
problem you have to the appropriate question on Stack Overflow.
Now I don't think it's quite that important, but it's a resource that
you'll probably use frequently as you become a more proficient Python scripter.
So here I am at the main tour page for Stack Overflow.
I recommend that you spend a few seconds to look over just to
understand how Stack Overflow works.
Probably the best way to kind of understand this is go back and
look at the first question that we had to answer,
which was how to convert a string into uppercase in Python.
And so the way you see this is laid out is here's a question posed by a user and
there's a number over here,
which is the number of other users that have liked this particular question.
So nearly 400 users say his is a nice question, I want to know how to do this.
And then down below are essentially a sequence of answers here,
there's six answers to this one.
And each answer essentially has the answer plus comments.
And the most important thing is there's a number here which says how many users
liked this answer.
So here, almost 700 users liked this answer.
So this is a very popular answer and one that you should probably look at, okay.
So, I've kind of discussed using Stack Overflow.
Now I'm going to give you a few caveats about using Stack Overflow.
The first one is that the code on Stack Overflow is licensed, so there's
restrictions on you copying this code into your program, so just be aware of that.
The second thing is don't use Stack Overflow as a substitute for thinking.
Read the answer and understand it so
that you don't need to make that same search again, so that you can then
work through that same problem next time without having to do a web search.
And finally understand that this is a resource for
professional programmers, so don't post your homework questions on here.
Wait untill you become an expert scripter, and
then when you're really truly stuck and you can't find
the answer to your important question, then you can post it there.
As you gain more expertise, then you can also answer other students' questions,
other programmers' questions.
But please, don't post your homework questions there, that's very bad form.
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