This document provides an introduction to Python programming through a series of exercises. It begins with definitions of Python and why it is useful. It then covers basic Python concepts like strings, lists, loops, functions and modules. The latter half provides 5 exercises to practice these concepts, such as printing messages, removing characters, using for loops and if/else statements, writing data to a JSON file, and generating stock data from an online API. The document aims to cover Python fundamentals in 90 minutes through hands-on learning.

1. Larry cai <larry.caiyu@gmail.com>

2.  What is python ? Why Python ?
 Exercise 1: Hello World
 Exercise 2: String, List via command line
 Exercise 3: For loop with if..else..
 Exercise 4: Learn how to use module json to dump data
 Exercise 5: Generate online NASDAQ data using json
!!! Lots of materials are copied from
http://www.cs.columbia.edu/~hgs/teaching/ap/slides/python.ppt and which is
based on official tutorial by Guido van Rossum
Exercises are created by Larry Cai
Python in 90 minutes2

3. What is Python ? And Why Python 2.7
 Python is an easy to learn, powerful script programming
language
 Python is mature and better community compare to Perl
 Python is high level over shell script
 Python is well supported in OS as default compare to
Ruby (which is also nice)
 Python 3.x is quite new, not well accepted
 Welcome to Python world
Python in 90 minutes3

4.  Python 2.7.x In Windows with Git Bash
 http://www.python.org/ftp/python/2.7.3/python-2.7.3.msi
 Add into Path
 How to run ?
 /usr/local/bin/python
 #!/usr/bin/env python
 interactive use
Python 2.7.3 (default,Apr 10 2012, 23:24:47) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>
 $ python script.py
Python in 90 minutes4

5.  Hello World
 hello.py
#!/usr/bin/env python
for name in [“larry”,”cai”]:
print "hello" , name
Python in 90 minutes5

6. Tips: Indent is important for python
 Visible symbol in your favorite editor
Python in 90 minutes6
Python forces to use a certainPython forces to use a certain
indentation style instead of “{,}”indentation style instead of “{,}”

7. Basic operations & program
 Assignment:
 size = 40
 a = b = c = 3
 Numbers
 integer, float
 complex numbers: 1j+3,
abs(z)
 Strings
 'hello world',
'it's hot'
 "bye world"
 continuation via or use """
long text """"
a,b = 0, 1
# non-zero = true
while b < 10:
# formatted output,
without n
print b,
# multiple assignment
a,b = b, a+b
Python in 90 minutes7

8. String & List operations
 concatenate with + or
neighbors
 word = 'Help' + x
 word = 'Help' 'a'
 subscripting of strings
 'Hello'[2]  'l'
 slice: 'Hello'[1:2]  'el'
 word[-1]  last character
 len(word)  5
 immutable: cannot assign to
subscript
 lists can be heterogeneous
 a = ['spam', 'eggs',
100, 1234, 2*2]
 Lists can be indexed and
sliced:
 a[0]  spam
 a[:2]  ['spam', 'eggs']
 Lists can be manipulated
 a[2] = a[2] + 23
 a[0:2] = [1,12]
 a[0:0] = []
 len(a)  5
Python in 90 minutes8

9. Learn the standard script sample
https://gist.github.com/4308811
Help doc
Import library
Function
Main func
Start here !
Python in 90 minutes9

10. Exercise 2: remove characters
 Practices basic operation in Interactive Shell
 Add features to remove two characters each from input
 ./hello2.py -m larry,cai
hello rry
hello i
Hints: nameHints: names = messages.split(“,”)s = messages.split(“,”)
Python in 90 minutes10

11. Control flow: if & for
x =
int(raw_input("Please
enter #:"))
if x < 0:
x = 0
print 'Negative
changed to zero'
elif x == 0:
print 'Zero'
elif x == 1:
print 'Single'
else:
print 'More'
 no case statement
a = ['cat', 'window',
'defenestrate']
for x in a:
print x, len(x)
 no arithmetic
progression, but
 range(10)  [0, 1, 2,
3, 4, 5, 6, 7, 8, 9]
 for i in
range(len(a)):
print i, a[i]
 do not modify the
sequence being iterated
over
Python in 90 minutes11

12. Loops: break, continue, else, o nothing
 break and continue
like C
 else after loop
exhaustion
for n in range(2,10):
for x in range(2,n):
if n % x == 0:
print n, 'equals',
x, '*', n/x
break
else:
# loop fell through
without finding a factor
print n, 'is prime'
 pass does nothing
 syntactic filler
while 1:
pass
Python in 90 minutes12

13. Exercise 3: for loop with if..else..
 ./hello2.py -m larry,cai,in,github
1. hello Larry
2. hello Cai
3. @
4. hello Github
Hints: think about loop in clean wayHints: think about loop in clean way
Python in 90 minutes13

14. Defining functions
def fib(n):
"""Print a Fibonacci
series up to n."""
a, b = 0, 1
while b < n:
print b,
a, b = b, a+b
>>> fib(2000)
 First line is docstring
 first look for variables in
local, then global
 need global to assign global
variables
def ask_ok(prompt,
retries=4, complaint='Yes
or no, please!'):
while 1:
ok = raw_input(prompt)
if ok in ('y', 'ye',
'yes'): return 1
if ok in ('n', 'no'):
return 0
retries = retries - 1
if retries < 0: raise
IOError, 'refusenik
error'
print complaint
>>> ask_ok('Really?')
Python in 90 minutes14

15. Modules
 import module:
import fibo
 Use modules via "name
space":
>>> fibo.fib(1000)
>>> fibo.__name__
'fibo'
 can give it a local name:
>>> fib = fibo.fib
>>> fib(500)
 function definition +
executable statements
 executed only when module
is imported
 modules have private symbol
tables
 avoids name clash for global
variables
 accessible as
module.globalname
 can import into name space:
>>> from fibo import fib,
fib2
>>> fib(500)
 can import all names defined
by module:
>>> from fibo import *
Python in 90 minutes15

16. Exercise 4: write into json config file
 JSON (JavaScript Object Notation) dump list of the
messages into external config files
 ./hello2.py -m larry,cai,in,github > config.json
 $ cat config.json
[
“larry”,
“cai”,
“in”,
“github”
]
Hints: json.dumps(data, indent=2)Hints: json.dumps(data, indent=2)
Python in 90 minutes16

17. Tuples and sequences
 lists, strings, tuples: examples
of sequence type
 tuple = values separated by
commas
>>> t = 123, 543, 'bar'
>>> t[0]
123
>>> t
(123, 543, 'bar')
 Tuples may be nested
>>> u = t, (1,2)
>>> u
((123, 542, 'bar'), (1,2))
 Empty tuples: ()
>>> empty = ()
>>> len(empty)
0
 sequence unpacking  distribute
elements across variables
>>> t = 123, 543, 'bar'
>>> x, y, z = t
>>> x
123
 packing always creates tuple
 unpacking works for any sequence
Python in 90 minutes17

18. Dictionaries
 like Tcl or awk associative
arrays
 indexed by keys
 keys are any immutable type:
e.g., tuples
 but not lists (mutable!)
 uses 'key: value' notation
>>> tel = {'hgs' : 7042, 'lennox':
7018}
>>> tel['cs'] = 7000
>>> tel
 no particular order
 delete elements with del
>>> del tel['foo']
 keys() method  unsorted list of
keys
>>> tel.keys()
['cs', 'lennox', 'hgs']
 use has_key() to check for existence
>>> tel.has_key('foo')
0
Python in 90 minutes18

19. Exercise 5: Generate report from internet
 Print MSFT, GOOG stock via Nasdaq live JSON with sort
 ./hello2.py –s MSFT,GOOG
“Getting live data from NASDAQ @ <current time>
GOOG: xx
MSFT: xx
$ curl -x <proxy> "http://finance.google.com/finance/info?client=ig&q=NASDAQ:MSFT,NASDAQ:GOOG “
fl = urlopen (“link”)
data = json.loads(contents)
[
{
"id": "694653"
,"t" : "GOOG"
,"e" : "NASDAQ"
,"l" : "701.96"
,"l_cur" : "701.96"
,"s": "0"
,"ltt":"4:00PM EST"
,"lt" : "Dec 14, 4:00PM EST"
,"c" : "-0.74"
,"cp" : "-0.10"
,"ccol" : "chr"
}
]
Hints: urlopen -> json.load -> data ..Hints: urlopen -> json.load -> data ..
Python in 90 minutes19

20.  Automate your daily work in python scripts
 Keep coding in python !!!
 Reading books and sample codes !!
Python in 90 minutes20

21.  Slides:
 http://www.slideshare.net/doughellmann/an-introduction-to-
the-zen-of-python - Doug Hellmann
 http://www.cs.columbia.edu/~hgs/teaching/ap/slides/python.ppt
 List books, articles, and electronic sources
 http://docs.python.org/2.7/
 Python cheatsheet: http://www.addedbytes.com/cheat-
sheets/python-cheat-sheet/
 Example for last exercise
 http://digitalpbk.com/stock/google-finance-get-stock-quote-realtime
Python in 90 minutes21