【C011】Python – 基礎教程學習（二）

 第三章：使用字串

基底字元串操作

 

>>> format = "Hello,%s,%s enough for ya?">>> values = ('world','Hot')>>> print format % valuesHello,world,Hot enough for ya?

>>> format = "Pi with three decimals: %.3f">>> from math import pi>>> print format % piPi with three decimals: 3.142

簡單轉換

 

 

>>> 'Price of eggs: $%d' % 42'Price of eggs: $42'>>> 'Hexadecimal price of eggs: %x' % 42'Hexadecimal price of eggs: 2a'>>> from math import pi>>> 'Pi: %f...' % pi'Pi: 3.141593...'>>> 'Very inexact estimate of pi: %i' % pi'Very inexact estimate of pi: 3'>>> 'Using str: %s' % 42L'Using str: 42'>>> 'Using repr: %r' % 42L'Using repr: 42L'

欄位寬度和精度

 

 

>>> '%10f' % pi'  3.141593'>>> '%10.2f' % pi'      3.14'>>> '%.5s' % 'Guido van Rossum''Guido'>>> '%.*s' % (5,'Guido van Rossum')    #可以通過運算式來自訂數字'Guido'

符號、對齊和0填充

 

 

>>> '%010.2f' % pi'0000003.14'>>> 0108>>> '%-10.2f' % pi'3.14      '

>>> print('%5d' % 10) + '\n' + ('%5d' % -10)   10  -10

>>> print('%+5d' % 10) + '\n' + ('%+5d' % -10)  +10  -10

3-1

 

 

# Print a formatted price list with a given widthwidth = input('Please enter width: ')price_width = 10item_width = width - price_widthheader_format = '%-*s%*s'format       = '%-*s%*.2f'print '=' * widthprint header_format % (item_width, 'Item', price_width, 'Price')print '-' * widthprint format % (item_width, 'Apples', price_width, 0.4)print format % (item_width, 'Pears', price_width, 0.5)print format % (item_width, 'Cantaloupes', price_width, 1.92)print format % (item_width, 'Dried Apricots (16 oz.)', price_width, 8)print format % (item_width, 'Prunes (4 lbs.)', price_width, 12)print '=' * width

字串方法

 

find

 

>>> 'With a moo-moo here, and a moo-moo there'.find('moo')7>>> title = "Monty Python's Flying Circus">>> title.find('Monty')0>>> title.find('Python')6>>> title.find('Flying')15>>> title.find('Xircus')-1>>> subject = '$$$ Get rich now!! $$$'>>> subject.find('$$$')0>>> subject.find('$$$',1)19>>> subject.find('!!')16>>> subject.find('!!',0,16)-1

join

 

 

>>> seq = ['1','2','3','4','5']>>> sep.join(seq)'1+2+3+4+5'>>> dirs = '','usr','bin','env'>>> '/'.join(dirs)'/usr/bin/env'>>> ''.join(seq)'12345'>>> print 'C:' + '\\'.join(dirs)C:\usr\bin\env

lower

 

 

>>> name = 'Gumby'>>> names = ['gumby','smith','jones']>>> if name.lower() in names: print 'Found it!'Found it!

replace

 

 

>>> 'This is a test'.replace('is','eez')'Theez eez a test'

split

 

 

>>> '1+2+3+4+5'.split('+')['1', '2', '3', '4', '5']>>> '/user/bin/env'.split('/')['', 'user', 'bin', 'env']>>> 'Using the default'.split()['Using', 'the', 'default']

strip（去除兩側的空格，或是符號）

 

 

>>> '        internal whitespace is kept        '.strip()'internal whitespace is kept'>>> names = ['gumby','smith','jones']>>> name = 'gumby'>>> if name.strip() in names: print 'Found it!'Found it!>>> '***SPAM * for * everyone!!! ***'.strip(' *!')'SPAM * for * everyone'

 

 第四章：字典：當索引不好用時

建立和使用字典

 

>>> phonebook = {'Alice':'2341','Beth':'9102','Cecil':'3258'}>>> phonebook['Alice']'2341'

dict函數

 

 

>>> items = [('name','Gumby'),('age',42)]>>> d = dict(items)>>> d{'age': 42, 'name': 'Gumby'}>>> d = dict(name = 'Gumby' , age = 32)>>> d{'age' : 32, 'name' : 'Gumby'}

基本字典操作

 

 

>>> x = {}>>> x[42] = 'Foobar'>>> x{42: 'Foobar'}

4-1 字典樣本

 

# A simple database# A dictionary with person names as keys. Each person is represented as# another dictionary with the keys 'phone' and 'addr' referring to their phone# number and address, respectively.people = {    'Alice': {        'phone': '2341',        'addr': 'Foo drive 23'    },    'Beth': {        'phone': '9102',        'addr': 'Bar street 42'    },    'Cecil': {        'phone': '3158',        'addr': 'Baz avenue 90'    }}# Descriptive labels for the phone number and address. These will be used# when printing the output.labels = {    'phone': 'phone number',    'addr': 'address'}name = raw_input('Name: ')# Are we looking for a phone number or an address?request = raw_input('Phone number (p) or address (a)? ')# Use the correct key:if request == 'p': key = 'phone'if request == 'a': key = 'addr'# Only try to print information if the name is a valid key in# our dictionary:if name in people: print "%s's %s is %s." % \    (name, labels[key], people[name][key])

>>> phonebook = {'Beth':'9102','Alice':'2341','Cecil':'3258'}>>> phonebook{'Beth': '9102', 'Alice': '2341', 'Cecil': '3258'}>>> phonebook['Alice']'2341'>>> "Cecil's phone number is %(Cecil)s." % phonebook"Cecil's phone number is 3258."

字典方法

clear

 

>>> d = {}>>> d['name'] = 'Gumby'>>> d['age'] = 42>>> d{'age': 42, 'name': 'Gumby'}>>> returned_value = d.clear()>>> d{}>>> print returned_valueNone>>> x = {}>>> y = x>>> x['key'] = 'value'>>> y{'key': 'value'}>>> x = {}>>> y{'key': 'value'}>>> x{}>>> x = {}>>> y = x>>> x['key'] = 'value'>>> y{'key': 'value'}>>> x.clear()>>> y{}>>> x = {}>>> x['key'] = 'value'>>> x{'key': 'value'}>>> x.clear()>>> x{}

copy（淺複製）（引用）

 

 

>>> x = {'username':'admin','machines':['foo','bar','baz']}>>> y = x.copy()>>> y['username'] = 'mlh'>>> y{'username': 'mlh', 'machines': ['foo', 'bar', 'baz']}>>> y['machines'].remove('bar')>>> y{'username': 'mlh', 'machines': ['foo', 'baz']}

deepcopy深複製（副本）

 

 

>>> from copy import deepcopy>>> d = {}>>> d['names'] = ['Alfred','Bertrand']>>> c = d.copy()>>> dc = deepcopy(d)>>> d['names'].append('Clive')>>> c{'names': ['Alfred', 'Bertrand', 'Clive']}>>> dc{'names': ['Alfred', 'Bertrand']}

fromkeys

 

 

>>> {}.fromkeys(['name','age']){'age': None, 'name': None}>>> dict.fromkeys(['name','age'],'Unknow'){'age': 'Unknow', 'name': 'Unknow'}

get

 

 

>>> d = {}>>> print d['name']Traceback (most recent call last):  File "<pyshell#67>", line 1, in <module>    print d['name']KeyError: 'name'>>> print d.get('name')None>>> d.get('name','N/A')'N/A'>>> d['name'] = 'Eric'>>> d.get('name')'Eric'

has_key

 

 

>>> d = {}>>> d.has_key('name')

>>> d = {'title':'Python Web Site','url':'http://www.python.org','spam':0}>>> d.items()[('url', 'http://www.python.org'), ('spam', 0), ('title', 'Python Web Site')]>>> it = d.iteritems()>>> it<dictionary-itemiterator object at 0x01F526F0>>>> list(it)[('url', 'http://www.python.org'), ('spam', 0), ('title', 'Python Web Site')]>>> 

False>>> d['name'] = 'Eric'>>> d.has_key('name')True>>>

 

items和iteritems

>>> d = {'title':'Python Web Site','url':'http://www.python.org','spam':0}>>> d.items()[('url', 'http://www.python.org'), ('spam', 0), ('title', 'Python Web Site')]>>> it = d.iteritems()>>> it<dictionary-itemiterator object at 0x01F526F0>>>> list(it)[('url', 'http://www.python.org'), ('spam', 0), ('title', 'Python Web Site')]>>> 

keys和iterkeys

pop

>>> d = {'x':1,'y':2}>>> d.pop('x')1>>> d{'y': 2}

popitem

>>> d = {'url':'http://www.python.org','spam':0,'title':'Python Web Site'}>>> d.popitem()('url', 'http://www.python.org')>>> 

setdefault

>>> d = {}>>> d.setdefault('name','N/A')'N/A'>>> d{'name': 'N/A'}>>> d['name'] = 'Gumby'>>> d.setdefault('name','N/A')'Gumby'>>> d{'name': 'Gumby'}>>> 

update

>>> d = {'title':'Python Web Site','url':'http://www.python.org','changed':'Mar 14 22:09:15 MET 2008'}>>> x = {'title':'Python Language Website'}>>> d.update(x)>>> d{'url': 'http://www.python.org', 'changed': 'Mar 14 22:09:15 MET 2008', 'title': 'Python Language Website'}>>> 

values和itervalues

>>> d = {}>>> d[1] = 1>>> d[2] = 2>>> d[3] = 3>>> d[4] = 1>>> d.values()[1, 2, 3, 1]>>> d{1: 1, 2: 2, 3: 3, 4: 1}>>>