Błyskawiczny kurs języka Python
- od podstaw do prostej strony opartej o
microframework Flask.
Marius Rejdak
[e-mail]
#inf.aei.polsl.pl @ QuakeNet
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Agenda
1. Filozofia języka
2. REPL
3. Podstawy języka
4. Klasy i obiekty
5. Wyjątki
6. Elementy funkcyjne
7. Debugowanie
8. Microframework Flask
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PEP 20 ą The Zen of Python
>>> import this
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
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http://xkcd.com/353/
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Learn the power of the Dark Side
REPL
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Pierwszy program
$ ./hello_world.py
$ python2 hello_world.py
Hello world!
Hello world!
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Operatory
lambda args: expr X + Y, X  Y
X if Y else Z X * Y, X % Y, X / Y, X // Y
X or Y -X, +X
X and Y ~X
not X X ** Y
X in Y, X not in Y X[i]
X is Y, X is not Y X[i:j:k]
X < Y, X <= Y X(& )
X > Y, X >= Y X.attr
X | Y (& )
X ^ Y [& ]
X & Y {& }
X << Y, X >> Y
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Dokumentowanie
>>> import os
>>> os.__doc__
"OS routines for Mac, NT, or Posix depending on what system
we're on.\n"
>>> def test():
... """Does nothing :)
... """
... pass
>>> test.__doc__
'Does nothing :)\n'
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Deklarowanie zmiennych,
Python jako język dynamicznie i
silnie typowany
foo = 1
a,b,c = ('a','b','c')
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Łańcuchy znaków (1)
>>> text = "A complex line of meaningless text"
>>> text
'A complex line of meaningless text'
>>> text2 = """Text line with > " <"""
>>> text2
'Text line with > " <'
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Łańcuchy znaków (2) ą Kodowanie i
unicode
>>> text = u"Krótki tekst"
>>> text = "Krótki tekst"
>>> text
>>> text
u'Kr\xf3tki tekst'
>>> print text
'Kr\xc3\xb3tki tekst'
Krótki tekst
>>> text.encode("utf-8")
>>> print text
'Kr\xc3\xb3tki tekst'
Krótki tekst
>>> text.decode("utf-8")
u'Kr\xf3tki tekst'
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Listy (1)
>>> li = ["a", "b", "c", 1, 2, -3]
>>> li
['a', 'b', 'c', 1, 2, -3]
>>> li[0]
'a'
>>> li[4]
2
>>> len(li)
6
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Listy (2) ą Ujemne indeksy
>>> li = ["a", "b", "c", 1, 2, -3]
>>> li
['a', 'b', 'c', 1, 2, -3]
>>> li[-1]
-3
>>> li[-2]
2
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Listy (3) ą Dodawanie elementów
>>> li
['a', 'b', 'c', 1, 2, -3]
>>> li.append("new")
>>> li
['a', 'b', 'c', 1, 2, -3, 'new']
>>> li.insert(2, "new2")
>>> li
['a', 'b', 'new2', 'c', 1, 2, -3, "new"]
>>> li.extend(["x", "y"])
>>> li
['a', 'b', 'new2', 'c', 1, 2, -3, 'new', 'x', 'y']
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Listy (4) ą Usuwanie elementów
>>> li
['a', 'b', 'c', 1, 2, -3]
>>> li.remove("c")
>>> li
['a', 'b', 1, 2, -3]
>>> li.remove(-3)
>>> li
['a', 'b', 1, 2]
>>> li.pop()
2
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Listy (5) ą Przeszukiwanie
>>> li
['a', 'b', 'c', 1, 2, -3]
>>> li.index("c")
2
>>> "x" in li
False
>>> "c" in li
True
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Listy (6) ą Operatory
>>> li = ["a", "b", "c"]
>>> li = li + ["x", "y"]
>>> li
['a', 'b', 'c', 'x', 'y']
>>> li = [1, 2] * 3
>>> li
[1, 2, 1, 2, 1, 2]
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Listy (7) ą Wycinanie
>>> li
['a', 'b', 'c', 1, 2, -3]
>>> li[1:3]
['b', 'c']
>>> li[1:-1]
['b', 'c', 1, 2]
>>> li[:3]
['a', 'b', 'c']
>>> li[3:]
[1, 2, -3]
>>> li[:]
['a', 'b', 'c', 1, 2, -3]
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Listy (8) ą Append a extend
>>> li = ['a', 'b', 'c']
>>> li.extend(['d', 'e', 'f'])
>>> li
['a', 'b', 'c', 'd', 'e', 'f']
>>> len(li)
6
>>> li[-1]
'f'
>>> li = ['a', 'b', 'c']
>>> li.append(['d', 'e', 'f'])
>>> li
['a', 'b', 'c', ['d', 'e', 'f']]
>>> len(li)
4
>>> li[-1]
['d', 'e', 'f']
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Krotka (ang. tuple)
>>> k = ("a", "b", "c")
>>> k
('a', 'b', 'c')
>>> k[0]
'a'
>>> k[-1]
'c'
>>> 'c' in k
True
>>> tuple([1, 2, 3])
(1, 2, 3)
>>> list((1, 2, 3))
[1, 2, 3]
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Słowniki (1)
>>> d = {}
>>> d["klucz"] = "wartosc"
>>> d["klucz"] = "inna wartosc"
>>> d
{'klucz': 'inna wartosc'}
>>> d["Klucz"] = "jeszcze inna wartosc"
>>> d
{'klucz': 'inna wartosc', 'Klucz': 'jeszcze inna wartosc'}
>>> del d['klucz']
>>> d.clear()
>>> d
{}
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Słowniki (2)
>>> d = {"k1": "w1", "k2": "w2"}
>>> d.items()
[('k2', 'w2'), ('k1', 'w1')]
>>> d.keys()
['k2', 'k1']
>>> d.values()
['w2', 'w1']
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if, elif, else
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Pętla for
>>> for i in ("a", "b", "c"):
... print i
a
b
c
>> for i in range(4):
... print i
0
1
2
3
>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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Pętla while
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Formatowanie łańcucha znaków
>>> a = "qwe"
>>> b = "rty"
>>> "%s zzz %s" % (a, b)
'qwe zzz rty'
>>> "Liczba: %d" % (1,)
'Liczba: 1'
>>> "Liczba zmiennoprzecinkowa: %.2f" % 12.3456
'Liczba zmiennoprzecinkowa: 12.34'
>>> ";".join(["x", "y", "z"])
'x;y;z'
>>> "x;y;z".split(";")
['x', 'y', 'z']
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Wyrażenia listowe (ang. list
comprehesion)
>>> li = [1, 9, 8, 4]
>>> [element*2 for element in li]
[2, 18, 16, 8]
>>> li
[1, 9, 8, 4]
>>> li = [elem*2 for elem in li]
>>> li
[2, 18, 16, 8]
>>> d = {"k1": "w1", "k2": "w2"}
>>> ["%s=%s" % (k, v) for k, v in d.items()]
['k2=w2', 'w1=w1']
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Filtrowanie list
>>> list = [1, 9, 8, 4]
>>> [element for element in list if element < 7]
[1, 4]
>>> [element**3 for element in list if element < 7]
[1, 64]
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Argumenty nazwane i opcjonalne
>>> def funkcja(arga, argb=1, argc=2):
... return arga + argb + argc
...
>>> funkcja(0)
3
>>> funkcja(0, 2)
4
>>> funkcja(0, 2, 5)
7
>>> funkcja(0, argc=1)
2
>>> funkcja(arga=0, argb=0, argc=0)
0
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Importowanie modułów
>>> import os
>>> os

>>> os.open

>>> from os import fork
>>> fork

>>> import os as os2
>>> from os import fork as fork2
>>> fork2

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Funkcja str
>>> str(1)
'1'
>>> li = ["a", "b", "c"]
>>> str(li)
"['a', 'b', 'c']"
>>> import os
>>> str(os)
""
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Funkcja dir
>>> import re
>>> dir(re)
['DEBUG', 'DOTALL', 'I', 'IGNORECASE', 'L', 'LOCALE', 'M', 'MULTILINE', 'S', 'Scanner', 'T', 'TEMPLATE', 'U',
'UNICODE', 'VERBOSE', 'X', '_MAXCACHE', '__all__', '__builtins__', '__doc__', '__file__', '__name__', '__package__',
'__version__', '_alphanum', '_cache', '_cache_repl', '_compile', '_compile_repl', '_expand', '_pattern_type',
'_pickle', '_subx', 'compile', 'copy_reg', 'error', 'escape', 'findall', 'finditer', 'match', 'purge', 'search',
'split', 'sre_compile', 'sre_parse', 'sub', 'subn', 'sys', 'template']
>>> dir(0)
['__abs__', '__add__', '__and__', '__class__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__',
'__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__',
'__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__',
'__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__',
'__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__',
'__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__',
'__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length',
'conjugate', 'denominator', 'imag', 'numerator', 'real']
>>> dir("")
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__',
'__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__',
'__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__',
'__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split',
'_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format',
'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower',
'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines',
'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
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Funkcja type
>>> type(0)

>>> type("a")

>>> import os
>>> type(os)

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Metody specjalne
__init__(self [, argumenty])
__repr__(self)
__str__(self)
__cmp__(self, arg)
__len__(self)
__call__(self [, argumenty])
__setitem__(self, key, item)
__getitem__(self, key)
__add__(self, arg)
...i wiele innych
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Wyrażenia lambda
>>> l = lambda x: x*2
>>> l(3)
6
>>> (lambda x: x*3)(3)
9
>>> (lambda x,y: x*y)(6,8)
48
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Definiowanie i inicjalizacja klas
>>> n = NazwaKlasy("a", "b")
>>> n.metoda()
a b
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Wyjątki
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Praca na plikach
>>> plik = open("plik.txt", "w")
>>> plik.write("test")
>>> plik.close()
>>> print open("plik.txt").read()
test
>>> plik = open("plik.txt", "a")
>>> plik.write(" test2")
>>> plik.close()
>>> print
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The Python Debugger
$ python -m pdb myscript.py
Breakpoint w kodzie:
import pdb; pdb.set_trace()
$ python -m ipdb myscript.py
import ipdb; ipdb.set_trace()
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Flask is Fun (1)
Instalacja
$ pip install Flask
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Flask is Fun (2)
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Flask is Fun (3)
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Ciekawe biblioteki

Frameworki webowe

Django

Pylons / Pyramids

CherryPy

Zope

SQLAlchemy

Pickle

BeautifulSoup

PyGTK, PyQt

Py2exe
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Polecane materiały

Książka ąDive into Python�

http://www.diveintopython.net/

http://pl.wikibooks.org/wiki/Zanurkuj_w_Pythonie

The Python Tutorial

http://docs.python.org/tutorial/