Post on 21-Jun-2020
On Python languageHow to use Python
Syntax of PythonTypes in Python
Outline
1 On Python language
2 How to use Python
3 Syntax of Python
4 Types in PythonSimple types in PythonCollectionsProcessing collectionsStringsTips
Marcin Młotkowski Object–oriented programming 1 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
The beginnings of Pythons
90 — CWI Amsterdam, Guido van Rossum
Marcin Młotkowski Object–oriented programming 2 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Current state
Python Software Foundation (PSF)
Marcin Młotkowski Object–oriented programming 3 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Current version
2.* (2.4, 2.6, 2.7.2)
3.* (3.2.2)
Marcin Młotkowski Object–oriented programming 4 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Why I like Python
Simple and clean syntax:
few keywords and operators;
indentation is obligatory
factorial
def fact(x):if x == 0:
return 1else :
return x * fact(x-1)
Marcin Młotkowski Object–oriented programming 5 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Why Python is so cool
Styles of programming
structural programming
object–oriented programming
functional programming
Marcin Młotkowski Object–oriented programming 6 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Why Python is so cool
Built-in types
Lists
vec = [1, 2, 3]doubled_vec = [ 2*e for e in vec]
Dictionaries
phone = { ’chris’ : 235711, ’Susie’ : 246810 }print tel[’susie’]
Marcin Młotkowski Object–oriented programming 7 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Why Python is so cool
Batteries included
I/O libraries
regular expressions
HTTP, HTML, XML
GUIs: pyGTK, wxPython, Tkinter, PythonWin
...
...
Marcin Młotkowski Object–oriented programming 8 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Other features of Python
Dynamic type system
>>> 2 + "two"Traceback (most recent call last):File "<stdin>", line 1, in ?
TypeError: unsupported operand type(s) for +: ’int’and ’str’>>>
Marcin Młotkowski Object–oriented programming 9 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Applications of Python
Projects
System tools (RedHat)
NASA
ZOPE/PLONE
http://www.python.org/about/success/
Marcin Młotkowski Object–oriented programming 10 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Outline
1 On Python language
2 How to use Python
3 Syntax of Python
4 Types in PythonSimple types in PythonCollectionsProcessing collectionsStringsTips
Marcin Młotkowski Object–oriented programming 11 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Interactive mode
$ python>>> 2+24>>> [1,2,3][-1:][3]Ctrl-d$
Marcin Młotkowski Object–oriented programming 12 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Execute a file
$ python a_file.py
What’s happened
1 program compilation (inc. syntax checking)
2 sometimes a file *.pyc is created
3 execute a program
Marcin Młotkowski Object–oriented programming 13 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Execute a file
$ python a_file.py
What’s happened
1 program compilation (inc. syntax checking)
2 sometimes a file *.pyc is created
3 execute a program
Marcin Młotkowski Object–oriented programming 13 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Execute a file
$ python a_file.py
What’s happened
1 program compilation (inc. syntax checking)
2 sometimes a file *.pyc is created
3 execute a program
Marcin Młotkowski Object–oriented programming 13 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Outline
1 On Python language
2 How to use Python
3 Syntax of Python
4 Types in PythonSimple types in PythonCollectionsProcessing collectionsStringsTips
Marcin Młotkowski Object–oriented programming 14 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Syntax
Assignment
four = 2 + 2x = y = z = 0name = ’Pyt’ + ’hon’primes = [2, 3, 5, 7]a, b = b, a+b
Marcin Młotkowski Object–oriented programming 15 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Syntax
Conditional statement
x = 4if x % 2 == 0:print "even"print "x = ", 2
x = 4if x % 2 == 0:print "even"
print "x = ", 2
Marcin Młotkowski Object–oriented programming 16 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Syntax
Conditional statement
x = 400if x % 2 == 0:if x > 100: print "large even"elif 10 < x <= 100:print "small even"
else:print "tiny even"
Marcin Młotkowski Object–oriented programming 17 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Logic expressions
false: 0, False, None, [],
true: True, nonempty values
conjunctions: and, or, not
operators: ==, !=, 1 < x < 2
Marcin Młotkowski Object–oriented programming 18 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Logic expressions
false: 0, False, None, [],
true: True, nonempty values
conjunctions: and, or, not
operators: ==, !=, 1 < x < 2
Marcin Młotkowski Object–oriented programming 18 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Logic expressions
false: 0, False, None, [],
true: True, nonempty values
conjunctions: and, or, not
operators: ==, !=, 1 < x < 2
Marcin Młotkowski Object–oriented programming 18 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Logic expressions
false: 0, False, None, [],
true: True, nonempty values
conjunctions: and, or, not
operators: ==, !=, 1 < x < 2
Marcin Młotkowski Object–oriented programming 18 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Loop statement
A statement while
a, b = 0, 1while b < 10:print ba, b = b, a + b
Marcin Młotkowski Object–oriented programming 19 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Loop statement
for in
a = [1,2,3,4]for e in a:print e
print "end"
Marcin Młotkowski Object–oriented programming 20 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Loop statements
for in
sum = 0for i in range(100):sum = sum + i
print "sum=", sum
Marcin Młotkowski Object–oriented programming 21 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Other statements
break and continue
empty statement: pass
while (True): pass
Marcin Młotkowski Object–oriented programming 22 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Functions
def foo(arg1, arg2=1, arg3=[3]):print arg1, arg2, arg3return 4
foo("one", 2)print foo(1, 2, 3)
Marcin Młotkowski Object–oriented programming 23 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Comments
def fun (arg):""" This is very important functionUse with high esteem"""
# end if empty argumentif arg == None: returnreturn arg
Marcin Młotkowski Object–oriented programming 24 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Input/output
Python 2.*
print "Hello world"x = input("Type x: ")y = input("Type y: ")print "x =", x, " y =", y
Python 3.0
print("Hello world")x = input("Type x: ")y = input("Type y: ")print("x =", x, " y =", y)
Marcin Młotkowski Object–oriented programming 25 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Input/output
Python 2.*
print "Hello world"x = input("Type x: ")y = input("Type y: ")print "x =", x, " y =", y
Python 3.0
print("Hello world")x = input("Type x: ")y = input("Type y: ")print("x =", x, " y =", y)
Marcin Młotkowski Object–oriented programming 25 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Tips
Editors with syntax highlighting: vim, gedit, emacs
Tools
idlePythonCard/codeEditor
"Executable"files and national characters:
file.py
#!/usr/bin/python# -*- coding: iso-8859-2 -*-
Marcin Młotkowski Object–oriented programming 26 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Tips
Editors with syntax highlighting: vim, gedit, emacs
Tools
idlePythonCard/codeEditor
"Executable"files and national characters:
file.py
#!/usr/bin/python# -*- coding: iso-8859-2 -*-
Marcin Młotkowski Object–oriented programming 26 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Tips
Editors with syntax highlighting: vim, gedit, emacs
Tools
idlePythonCard/codeEditor
"Executable"files and national characters:
file.py
#!/usr/bin/python# -*- coding: iso-8859-2 -*-
Marcin Młotkowski Object–oriented programming 26 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Why "Python"?
Marcin Młotkowski Object–oriented programming 27 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Further reading
www.python.org
"Dive into Python", Mark Pilgrim
...
Marcin Młotkowski Object–oriented programming 28 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Outline
1 On Python language
2 How to use Python
3 Syntax of Python
4 Types in PythonSimple types in PythonCollectionsProcessing collectionsStringsTips
Marcin Młotkowski Object–oriented programming 29 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Simple types
simple types: integers, floats, booleans
sequential types: strings, lists, tuples
Marcin Młotkowski Object–oriented programming 30 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
”Simple” integers
Range: [−sys.maxint − 1, sys.maxint]
Operators: +, - , /, //, %, **
Standard functions: abs(x), divmod(x, y) = (x // y, x % y)
Warning
Dividing integer by integer gives integer
4//3 = 1
Marcin Młotkowski Object–oriented programming 31 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Integers and conversions
(1.0 ∗ 4)//3 = 1.0
(1.0 ∗ 4)/3 = 1.33333333333333
float(4)/3 = 4/float(3)
Marcin Młotkowski Object–oriented programming 32 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Large integers
Example
>>> 1000 ** 101000000000000000000000000000000L>>> long(100)100L
Marcin Młotkowski Object–oriented programming 33 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Constants
Integers0x123, 0x123456789L, 0123, 06789L
Floats3.14 10. .002 .271e1
Marcin Młotkowski Object–oriented programming 34 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Complex numbers
Literals and expressions1 + 3jx + 12jcomplex(x,0)
Operatorsx.real ∗ ∗2 + y.imag ∗ ∗2
Marcin Młotkowski Object–oriented programming 35 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Standard numerical libraries
math
import mathprint math.cos(3.14)
random
from random import *print random()
Marcin Młotkowski Object–oriented programming 36 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Examples
Lists: [12,3]
Strings: "abc", ’def’, u’Zazółc zółta jazn’
tuples: (1, ”one”, (1, 2+3j, 0x4))
dictionaries
Sets
Marcin Młotkowski Object–oriented programming 37 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Tuple
brown = 165, 42, 42NavyBlue = (0,0,128)htmlColor = { ’turquoise’ : (64,224,208), ’NavyBlue’ :NavyBlue }r, g, b = htmlCol[’NavyBlue’]
Marcin Młotkowski Object–oriented programming 38 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Reminder
assignment
(
a, b
)
=
(
1, 2
)
Marcin Młotkowski Object–oriented programming 39 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Reminder
assignment
(a, b)= (1, 2)
Marcin Młotkowski Object–oriented programming 39 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Inclusion operator
in
’bc’ in ’abcd’4 not in [2, 3, 5, 7, 11]’pi’ in { ’pi’ : 3.1415, ’e’ : 2.7182 }
Marcin Młotkowski Object–oriented programming 40 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Collection operators
+
>>> [ ’one’, 2, 3.0 ] + [ 0x4, 05 ][’one’, 2, 3.0, 4, 5]>>> (’one’, 2, 3.0) + (0x4, 05)(’one’, 2, 3.0, 4, 5)
Marcin Młotkowski Object–oriented programming 41 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Size of collection
len
len( [’one’, 2, 3.0] )len( {’one’ : 1, ’two’ : 2 } )len( (1, 2, 3) )
Marcin Młotkowski Object–oriented programming 42 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Elements of collections
[1, 2, 3][2] = 3
’abcd’[1:3] = ’bc’(1, 2, 3)[1:] = (2, 3)(1,2,3)[:1] = (1, )’Python’[:-1] = ’Pytho’’Python’[-1:] = ’Python’[-1] = ’n’
Marcin Młotkowski Object–oriented programming 43 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Elements of collections
[1, 2, 3][2] = 3’abcd’[1:3] = ’bc’
(1, 2, 3)[1:] = (2, 3)(1,2,3)[:1] = (1, )’Python’[:-1] = ’Pytho’’Python’[-1:] = ’Python’[-1] = ’n’
Marcin Młotkowski Object–oriented programming 43 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Elements of collections
[1, 2, 3][2] = 3’abcd’[1:3] = ’bc’(1, 2, 3)[1:] = (2, 3)
(1,2,3)[:1] = (1, )’Python’[:-1] = ’Pytho’’Python’[-1:] = ’Python’[-1] = ’n’
Marcin Młotkowski Object–oriented programming 43 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Elements of collections
[1, 2, 3][2] = 3’abcd’[1:3] = ’bc’(1, 2, 3)[1:] = (2, 3)(1,2,3)[:1] = (1, )
’Python’[:-1] = ’Pytho’’Python’[-1:] = ’Python’[-1] = ’n’
Marcin Młotkowski Object–oriented programming 43 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Elements of collections
[1, 2, 3][2] = 3’abcd’[1:3] = ’bc’(1, 2, 3)[1:] = (2, 3)(1,2,3)[:1] = (1, )’Python’[:-1] = ’Pytho’
’Python’[-1:] = ’Python’[-1] = ’n’
Marcin Młotkowski Object–oriented programming 43 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Elements of collections
[1, 2, 3][2] = 3’abcd’[1:3] = ’bc’(1, 2, 3)[1:] = (2, 3)(1,2,3)[:1] = (1, )’Python’[:-1] = ’Pytho’’Python’[-1:] = ’Python’[-1] = ’n’
Marcin Młotkowski Object–oriented programming 43 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Slicing
>>> ’informatics’[::3]’ioac’
Marcin Młotkowski Object–oriented programming 44 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Iterations over collections
x = [1,2,3]y = [4,5,6]prod = 0for i in range(len(x)):
prod += x[i] * y[i]
Marcin Młotkowski Object–oriented programming 45 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
List processing
x = [1,2,3]y = [4,5,6]prod = 0for i, v in enumerate(x):
prod += v * y[i]print prod
Marcin Młotkowski Object–oriented programming 46 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
List processing, other implementation
x = [1,2,3]y = [4,5,6]prod = 0for a, b in zip(x, y):
prod += a * bprint prod
Marcin Młotkowski Object–oriented programming 47 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Dictionary processing
iteration
dict = { ’uno’ : 1, ’duo’ : 2, ’tre’: 3 }for key, val in dict.iteritems():
print key, "=", val
Marcin Młotkowski Object–oriented programming 48 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Constants
’Alice has a cat’“Alice has a cat”
Unicode
uZazółc zółta jazn""Zazółc zółta jazn"
Unicode
len(u"zółty") == 5len("zółty") == 8
Long strings
"""This is amultiline string""""
Marcin Młotkowski Object–oriented programming 49 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Constants
’Alice has a cat’“Alice has a cat”
Unicode
uZazółc zółta jazn""Zazółc zółta jazn"
Unicode
len(u"zółty") == 5len("zółty") == 8
Long strings
"""This is amultiline string""""
Marcin Młotkowski Object–oriented programming 49 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Constants
’Alice has a cat’“Alice has a cat”
Unicode
uZazółc zółta jazn""Zazółc zółta jazn"
Unicode
len(u"zółty") == 5len("zółty") == 8
Long strings
"""This is amultiline string""""
Marcin Młotkowski Object–oriented programming 49 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Constants
’Alice has a cat’“Alice has a cat”
Unicode
uZazółc zółta jazn""Zazółc zółta jazn"
Unicode
len(u"zółty") == 5len("zółty") == 8
Long strings
"""This is amultiline string""""
Marcin Młotkowski Object–oriented programming 49 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
Strings
Strings are collections
’raw’ strings: r’abcd\n’
String continuation:"This is a \n\very long string\n"
A lot of library functions
Strings are immutable, ie. ’abc’[1] = ’d’
Marcin Młotkowski Object–oriented programming 50 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
String formatting
Operator %
print "%i + %i = %i\n" % (2, 2, 2+2)
dict = { ’two’ : 2, ’four’ : 4 }print "%(two)s + %(two)s = %(four)s\n" % dict
Marcin Młotkowski Object–oriented programming 51 / 52
On Python languageHow to use Python
Syntax of PythonTypes in Python
Simple types in PythonCollectionsProcessing collectionsStringsTips
First aid
Interactive mode
>>> type(3.1415)<type ’float’>>>> dir(float)....>>> dir(3.1415)....>>> float.__doc__
Marcin Młotkowski Object–oriented programming 52 / 52