The document discusses Python programming concepts like running Python programs, the Python virtual machine, importing and reloading modules, and taking input. It provides examples of running Python code from the interactive shell and command line, how the .py and .pyc files work, and importing modules and functions from different files. The document also presents a practice problem on generating the Fibonacci sequence.

1. Python meetup -2
Vic Yang

2. How to run a
program?
Python Virtual Machine

3. Program Execution
In interactive shell:
print ‘hello world’ # hello world
print 2 ** 100 # 1267650600228229491496703205376
In command line:
python hello.py

4. Python Virtual Machine
.py VS. .pyc
1. .py is the source code of Python
2. .pyc is the byte-compiled code of .py
3. .pyc can be executed in PVM

5. Python Virtual Machine
.py .pyc PVM
source byte code execution
PVM is a huge loop that executes our code one by one.

6. .pyc
A file contains byte-code interpreted from .py
Boost the execution time.
Rebuild automatically if .py changed.
The text in .pyc file is not binary code.

7. Python Implementation
CPython - ported from ANSI C, standard
implementation.
Jython - compiled Python code to Java byte-
code and executed on JVM
IronPython - similar as Jython implemented

8. Input
commands

9. Input
standard input
a = “hello world”
print a
a = raw_input()
print a
sys.argv[1]
import sys
print sys.argv[1]
> python script1.py
script1.py

10. Module import and reload
script4.py
print ‘hello world’
print 2 ** 100
title = ‘The Meaning
of life’
IDLE
>>>import script4
>>>reload(script4)
>>>print script4.title

11. Module import and reload
threenames.py
a = ‘dead’
b = ‘parrot’
c = ‘sketch’
print a, b ,c
IDLE
>>>import three names
>>>threenames.b,
threenames.c
>>>from threenames
import a, b, c

12. Practice

13. Practice
Fibonacci sequence
CheckIO

14. Fibonacci sequence
def fib():
x = 0
y = 1
while 1:
yield x
x, y = y, x + y
!
g = fib()
for i in range(9):
print g.next()