Python Programming 1 2008926 JauJi Lin Outline Python

Python Programming 1 2008/9/26 Jau-Ji Lin

Outline • Python setup • Running Python programs • Basic data type in Python

Download and installation • http: //www. python. org/ • The current production version is 2. 5. 2

Running python programs • • Interactive coding System command lines Clicking file icons IDLE user interface

Interactive coding • Start -> All Programs -> Python 2. 5 -> Python (command line) • Start -> Run -> type ‘cmd’ -> type ‘python’ in python directory • Start -> All Programs -> Python 2. 5 -> IDLE (Python GUI)

Your first python program! • • • print ‘hello, world’ print 2 ** 8 myname = ‘george’ myname 2 ** 8

Interactive coding • For trying out pieces of python codes and seeing what happens. • The code you type is never stored in a file, you can’t run it again without retyping it.

System command lines • Start your favorite text editor, and type two python statements into a text file named hello. py: print 2 ** 8 print ‘hello, ’ + ‘world’ • C: Python 25>python hello. py

Clicking file icons • script 4. py # A comment import sys print sys. platform print 2 ** 100

Clicking file icons • script 5. py # A comment import sys print sys. platform print 2 ** 100 raw_input() Trick!

The IDLE user interface • Intergrated Deve. Lopment Environment • Python shell with syntax highlighting • Text editor with syntax highlighting, autocompletion, smart indent • Integrated debugger

The overall Python picture • • • Modules Statements Expression Objects In Python, we do ‘things’ with ‘stuff’. Things refer to the operation, and stuff refers to the objects on which we perform the operations

Python data types • • • Numbers Strings Lists Dictionaries Tuples Files

Numbers • • 123 + 222 1. 5 * 4 2 ** 100 3. 1415 * 2 print 3. 1415 * 2 import math. pi

Numbers • math. sqrt(85) • random() • random. choice([1, 2, 3, 4])

Strings • • S = ‘spam’ len(S) S[0] S[1] S[-2] S S[1: 3]

Strings • • S. find(‘pa’) S. replace(‘pa’, ‘XYZ’) line = ‘aaa, bbb, ccccc, dd’ line. split(‘, ’) S = ‘spam’ S. upper() S. isalpha()

Strings • • line = ‘aaa, bbb, ccccc, ddn’ line = line. rstrip() dir(S) help(S. index)

Lists • • L = [123, 'spam', 1. 23] len(L) L[0] L[: -1] L + [4, 5, 6] L. append(‘NI’) L. pop(2)

Lists • • • M = [‘bb’, ‘cc’, ‘aa’] M. sort() M. reverse() L[99] = 1

Lists • M = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ] • M[1][2] • col 2 = [row[1] for row in M]

Lists • • [row[1] + 1 for row in M] [row[1] for row in M if row[1] % 2 == 0] diag = [M[i][i] for i in [0, 1, 2]] doubles = [c * 2 for c in 'spam']

Dictionaries • • D = {'food': 'Spam', 'quantity': 4, 'color': 'pink'} D[‘food’] D[‘quantity’] += 1 D = {} D[‘name’] = ‘Bob’ D[‘job’] = ‘dev’ D[‘age’] = 40

Dictionaries • rec = {'name': {'first': 'Bob', 'last': 'Smith'}, 'job': ['dev', 'mgr'], 'age': 40. 5} • rec['name']['last'] • rec['job'][-1] • rec['job']. append('janitor') • rec = 0

Dictionaries • • D = {'a': 1, 'b': 2, 'c': 3} Ks = D. keys() for key in Ks: print key, '=>', D[key] for key in sorted(D): print key, '=>', D[key] for c in 'spam': print c. upper() D['e'] = 99 D['f'] D. has_key('f')

Tuples • • • An immutable list T = (1, 2, 3, 4) len(T) T + (5, 6) T[0] = 2

Files • • f = open('data. txt', 'w') f. write('Hellon') f. write('worldn') f. close()

Files • • f = open('data. txt') bytes = f. read() print bytes. split()

Exercise • Go to the PDB website and downlaod a pdb structure file, ex. 1 crn • Edit the file and delete all the data except the ‘ATOM’ records • Read in the file, and use the objects taught today to represent the data