This course will become read-only in the near future. Tell us at community.p2pu.org if that is a problem.
With Python, learning to program is easy and fun! Many Python programs are clear and concise, reading like plain English. This course will cover the fundamental aspects of Python including data types, flow control, encapsulation, inheritance, and helpful tools from the Python standard library.
Lets look at three components of many programming languages.
Three primary tools we will be working with are:
These three aspects are fundamental to programming in general and will be explored throughout this course.
Examples:
In Python, statements can take many forms and work with many programming elements such as names and operators.
Names are labels that point to a specific item in the computer's memory. Assignment statements are statements where we assign a name to a value, or memory location. Below, a_name points to the memory location of a_value.
>>> a_name = 'a_value'
Names, technically called identifiers, must start with an underscore (the "_" character) or a letter. Names can contain any sequence of letters, numbers, and underscores. Names cannot contain spaces or other special characters. Names are case sensetive, so 'Sunshine' and 'SUNSHINE' are two different names.
There are 33 reserved words that may not be used as names. The following table outlines Python's reserved words.
| False | None | True | and | assert |
| break | class | continue | def | del |
| else | except | finally | for | from |
| global | import | in | is | lambda |
| nonlocal | not | pass | raise | return |
| try | while | with | ||
Expressions typically return some result. The result can then be assigned a name.
In the following example, the expression on the right hand side will be evaluated and then assigned to the name to the left of the '=' assignment operator.
>>> total = 35.9 + 24.29 >>> total 60.19
Basic examples of expressions include arithmetic operations. Operators are included in expressions and consist of symbols such as:
| + | - | / | * | ** |
Here are some operators in action:
>>> 2 + 3 # Addition 5 >>> 3 - 2 # Subtraction 1 >>> 5 * 5 # Multiplication 25 >>> 10 / 5 # Division 2 >>> 3 ** 3 # Exponent 27
If you have any questions or difficulties post them here and we will work together to make sure that everyone has a positive learning experience. Please also post ideas and insights into these concepts. We can learn a lot from each others' perspectives and experience :-)
I have both Python 2 and 3 (on Ubuntu 10). If I deinstall Python2 totally via Synaptic Package Manager, would it affect any of the packages for Py3?
Also, when I run the following
name = input ('What is your name?\n')
print ('Hello ',name,'!')
it gives an unwanted space before '!'. How can I get rid of the space?
I have a question. I completed the first exercise (Chap 2- 'Variables, expressions, and statements') using Python 2.6 (on LINUX), which I had installed some time ago. I decided to install Python 3.2, which I did today and tried the first exercise again. I got the error message: NameError: name 'raw_input' is not defined. In fact, none of the command lines, such as 'print', does not work in 3.2. Could someone explain to me what is going on? Thank you.
raw_input() was renamed to input ().
print statement has been replaced with a print () function.
For details, search (cntr+f) for 'input' and 'print' on
Exercises 2.2-2.3-2.4-2.5 separated by comments :
http://pastebin.com/WzzTcUaT
Is anyone having difficulty copying their assignments and posting/pasting to somewhere? I've got Python installed, working, and not able to copy/cut/paste etc. I can take a screen shot, but I imagine by the time I get to writing the Nobel Prize winning code for something, it won't fit on my screen.
Do you know if you are using IDLE as an editor? IDLE opens in a window with "Python Shell" in the top blue bar and on the taskbar button, has familiar Windows options at top (File, Edit , etc)?
If so, you should be able to select text and use keyboard shortcuts to copy (Ctrl + C), but you can't right-click for such editing options.
If you're not using IDLE, as a new user, I recommend trying to find it. Hopefully you can find it in your start menu under All Programs > Python > IDLE.
Oh, deflation!
I had done exercise 1, assignment whatever aka 2.2, which is slide 25 by the way according to everyone else's assignment.
I did it. It worked. But, there is no "copy" feature from which I could paste it here. Also, there are no line numbers showing when I write code. Any hints?
To copy the code to say a service like pastebin, you can just select all the code and press the button combination Ctrl + V in pastebin. In regards to the line numbers, what editor or IDE are you using? If it is IDLE, I don't think the feature actually exists in IDLE. You could choose to use another editor such as Notepad ++ but be wary of mixing tabs and spaces when indenting.
I have reviewed the assignments posted by the three or four previous commenters. I wonder why they are taking Python 101? Obviously they have some background knowledge and are applying it quite well. Is there a Python Beginner A level 1 Pre-Computer Age course?
Okay, so back in CaveMan Days our teacher, Og, told us this: Do assignment 1. Furthermore, he told us what the assignment was: "Make a spatula out of a rock." However, here at Task 2 I have no idea what the assignments are. I'm told to do the exercises, but I find no exercises. I have copied the program samples shown in the slide show/streaming video. I can make more sense of Python than of the English explanations. Can someone tell me what the exercises cum assignments are?
Chapter 2 of Python for Informatics has some exercises.
I didn't realize that there was so much incompatibility between Python 2.x and Python 3.x. A few weeks ago, I started learning Python through Project Euler, and I've done about 20 problems so far. On my computers, the default "python" is Python 2, and you have to run scripts with "python3" to use Python 3. So I'd been learning Python 2, but decided to try 3 for this. There were a lot more hangups than I expected! Just something to be aware of.
For these exercises, the relevant things include:
There is a utility, called 2to3, that will convert programs from Python 2 to Python 3.
http://docs.python.org/library/2to3.html
My exercices http://pastebin.com/6s9wNa6M
I think my code could be improved.
Please, give me some feedback.
Thank you
EmperiuM
(exercises 2.2, 2.3, 2.4 and 2.5)
Hi. Your code is good and well commented. Although you can make 1 minor improvement.
Using a space on both sides of the equal two sign while assigning is a Good practice and increases readibility.
a=1 #NO a = 1 #YES
OK, thank you for telling me that. I'll keep that in mind for the future and I'll change on this code.
If you want to know other best practices you could read PEP-8: http://www.python.org/dev/peps/pep-0008/
Thank you mate :) I'll read it :)
Pastie to my answer set:
My py4int exercise 2 code
Exercise 2.2
name = raw_input('Enter your name: ')
print 'Hello', name
Exercise 2.3
# Get hours from the user
hours = raw_input('Enter number of hours: ')
f_hours = float(hours)
# Get rate from the user
rate = raw_input('Enter rate per hour: ')
f_rate = float(rate)
# Calculate pay
pay = f_hours * f_rate
# Output calculated pay
print 'Gross pay:',pay
Exercise 2.4
width = 17 height = 12.0 print width/2 # Result 8 (int) print width/2.0 # Result 8.5 (float) print height/3 # Result 4.0 (float) print 1 + 2 * 5 # Result 1+(2*5) -> 1+10 -> 11
Exercise 2.5
inp = raw_input('Enter temperature in Celsius: ')
temp_c = float(inp)
temp_f = (9.0 / 5.0) * temp_c + 32
print 'Temperature in Fahrenheit is:', temp_f