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?????2. ???Python?????? ?????Python ??? ??? 4. ??????
????
???????????У?????????????????????????????????“>>> ”??“.. ”????????????Щ???????????????????????????????е???У?????????????????У???????????????????????????????е??????????????????????????????????????????????С?
??????е???????????????????????Щ???????????????С?Python?е?????????“#”?????????????е??β???????????????е??????????????????????????????????????????У???????е?#???????#???
?????
# this is the first comment SPAM = 1 # and this is the second comment # ... and now a third! STRING = "# This is not a comment."
???????????Щ????Python???䶮?????????????????????“>>> ”????????ò?????????
?????????????????????????????????????????????????????????????????????????????+??-??*??/???????????е??÷??????????C??Pascal??????????????顣???磺
>>> 2+2 4 >>> # This is a comment ... 2+2 4 >>> 2+2 # and a comment on the same line as code 4 >>> (50-5*6)/4 5 >>> # Integer division returns the floor: ... 7/3 2 >>> 7/-3 -3
??c?????????“=”????????????????????????????????
>>> width = 20 >>> height = 5*9 >>> width * height 900
?????????????????????????
>>> x = y = z = 0 # Zero x, y and z >>> x 0 >>> y 0 >>> z 0
Python?????????????????????????????????????????????????????????????
>>> 3 * 3.75 / 1.5 7.5 >>> 7.0 / 2 3.5
??????????????????鲿????????“j”????“J”??????????з??????????????“(real+imagj)”??????????????“complex(real, imag)”??????????
>>> 1j * 1J (-1+0j) >>> 1j * complex(0,1) (-1+0j) >>> 3+1j*3 (3+3j) >>> (3+1j)*3 (9+3j) >>> (1+2j)/(1+1j) (1.5+0.5j)
????????????????鲿??????????????????????? z.real
?? z.imag
???????z????????鲿??
>>> a=1.5+0.5j >>> a.real 1.5 >>> a.imag 0.5
??????????????????????????float(), int() ?? long()?????????????????????????????????????????????????????abs(z)??????????????????z.real????????????
>>> a=3.0+4.0j >>> float(a) Traceback (most recent call last): File "<stdin>", line 1, in ? TypeError: can't convert complex to float; use e.g. abs(z) >>> a.real 3.0 >>> a.imag 4.0 >>> abs(a) # sqrt(a.real**2 + a.imag**2) 5.0 >>>
???????￡??????α????????????_?????С?????ζ???Python?????????????????????????????????????????????磺
>>> tax = 12.5 / 100 >>> price = 100.50 >>> price * tax 12.5625 >>> price + _ 113.0625 >>> round(_, 2) 113.06 >>>
???????????????????????????????????????????????Python????Ч?????????????????????????????????
?????????Python?????????????????????????????????????????????????????
>>> 'spam eggs' 'spam eggs' >>> 'doesn\'t' "doesn't" >>> "doesn't" "doesn't" >>> '"Yes," he said.' '"Yes," he said.' >>> "\"Yes,\" he said." '"Yes," he said.' >>> '"Isn\'t," she said.' '"Isn\'t," she said.'
?????????????????????С????????м??б???????????????????????????е??????????
hello = "This is a rather long string containing\n\ several lines of text just as you would do in C.\n\ Note that whitespace at the beginning of the line is\ significant." print hello
??????? \n ?????????б?????????б????newline????д“n”???????????з???????????????????
This is a rather long string containing several lines of text just as you would do in C. Note that whitespace at the beginning of the line is significant.
??????????????????“raw”?У?\n???о?????????У????????????б?????з?n?????????????е??????????????????
hello = r"This is a rather long string containing\n\ several lines of text much as you would do in C." print hello
???????
This is a rather long string containing\n\ several lines of text much as you would do in C.
???????????????????????????”””??'''????????????????е??????????β????????б??????е??????????????????С?
print """ Usage: thingy [OPTIONS] -h Display this usage message -H hostname Hostname to connect to """
produces the following output:
Usage: thingy [OPTIONS] -h Display this usage message -H hostname Hostname to connect to
?????????????????????????????????????????????????????÷?б?????????????????????????????????? ???????????а??????????????????????????????????????????????????????????????????print??????????????д?????????б????????????
???????????+?????????????????????????*???????
>>> word = 'Help' + 'A' >>> word 'HelpA' >>> '<' + word*5 + '>' '<HelpAHelpAHelpAHelpAHelpA>'
??????????????????????????????????п???д??“word = 'Help' 'A'”?????????????????Ч???κ???????????????????????????
>>> import string >>> 'str' 'ing' # <- This is ok 'string' >>> string.strip('str') + 'ing' # <- This is ok 'string' >>> string.strip('str') 'ing' # <- This is invalid File "<stdin>", line 1, in ? string.strip('str') 'ing' ^ SyntaxError: invalid syntax
????????????±????????????????C????????????????????±???0????????ж???????????????????????С?????????????????Icon????????????????????????????????????????????e????????????
>>> word[4] 'A' >>> word[0:2] 'He' >>> word[2:4] 'lp'
??????????????????????????????????0??????????????????????????????????
>>> word[:2] # The first two characters 'He' >>> word[2:] # All but the first two characters 'lpA'
??C??????????Python??????????д?????????????????????????
>>> word[0] = 'x' Traceback (most recent call last): File "<stdin>", line 1, in ? TypeError: object doesn't support item assignment >>> word[:1] = 'Splat' Traceback (most recent call last): File "<stdin>", line 1, in ? TypeError: object doesn't support slice assignment
????????????????Ч????????????μ????????
>>> 'x' + word[1:] 'xelpA' >>> 'Splat' + word[4] 'SplatA'
????????????????????????? s[:i]
+ s[i:] ????s??
>>> word[:2] + word[2:] 'HelpA' >>> word[:3] + word[3:] 'HelpA'
???????????????????????????????????????????????С??????????????????????
>>> word[1:100] 'elpA' >>> word[10:] '' >>> word[2:1] ''
???????????????????????????????磺
>>> word[-1] # The last character 'A' >>> word[-2] # The last-but-one character 'p' >>> word[-2:] # The last two characters 'pA' >>> word[:-2] # All but the last two characters 'Hel'
????-0????0??????????????????????
>>> word[-0] # (since -0 equals 0) 'H'
???????????????????????????????????????????????????????????
>>> word[-100:] 'HelpA' >>> word[-10] # error Traceback (most recent call last): File "<stdin>", line 1, in ? IndexError: string index out of range
??????????÷????????????????????????????????????????0????????е?n????????????????n?????磺
+---+---+---+---+---+ | H | e | l | p | A | +---+---+---+---+---+ 0 1 2 3 4 5 -5 -4 -3 -2 -1
?????????????и?????0??5??????????λ???????????????????????i??j?????????????????????????ɡ?
??????????????????????????????䶮???磬word[1:3]???????2??
???ú??? len() ??????????????
>>> s = 'supercalifragilisticexpialidocious' >>> len(s) 34
??Python2.0??????????????????????μ????????????洢????????Unicode ??????????????洢????Unicode?????????? http://www.unicode.org/ ?????????????????????????????????????е??????????????????
Unicode????????????????????е??????????????С? ??????????????256??????????????????????????????????????????????????????????????internationalization???????д??“i18n”????“i”+18 characters +“n”????Unicode??????????????????????????????????????
Python?ж??????Unicode????????????????????????????
>>> u'Hello World !' u'Hello World !'
?????Сд??“u”????????????????Unicode????????????????????????????????????Python?? Unicode-Escape ???????????????
>>> u'Hello\u0020World !' u'Hello World !'
???滻?? \u0020
???????????λ?ò???????? 0x0020
?? Unicode?????????????
?????????????????????Unicode??????????????????????????Latin-1???????????????????Unicode????????256???????Lation-1???????????????????
????????????????????????????????????Python??Raw-Unicode-Escape ??????????????????????????? ur ?????????Сд“u”??????в???????б???????????Щ?????? \uXXXX ????Unicode?????
>>> ur'Hello\u0020World !' u'Hello World !' >>> ur'Hello\\u0020World !' u'Hello\\\\u0020World !'
????????????????????б????????????????????????????
?????Щ??????????????Python?????????????????????????????????Unicode???????
???ú???unicode() ??????????????????????????Unicode?????????????????????????? Latin-1, ASCII, UTF-8, ?? UTF-16????????????????????????????????byte?洢Unicode????? ??????????? ASCII ?????????0??127???????????????????????????????????Unicode????????????д??????????str()????????????滻????????
>>> u"abc" u'abc' >>> str(u"abc") 'abc' >>> u"äöü" u'\xe4\xf6\xfc' >>> str(u"äöü") Traceback (most recent call last): File "<stdin>", line 1, in ? UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-2: ordinal not in range(128)
??????Unicode??????????????????????8λ??????????????Unicode????????encode()?????????????????????????????????????????Сд??
>>> u"äöü".encode('utf-8') '\xc3\xa4\xc3\xb6\xc3\xbc'
??????????????????????????????????Unicode????????????????uncode()?????????????????????????????
>>> unicode('\xc3\xa4\xc3\xb6\xc3\xbc', 'utf-8') u'\xe4\xf6\xfc'
Python ???????????????????????????????????????????????????????д????????????????????????????????????????????????????
>>> a = ['spam', 'eggs', 100, 1234] >>> a ['spam', 'eggs', 100, 1234]
???????????????????????????????????????????
>>> a[0] 'spam' >>> a[3] 1234 >>> a[-2] 100 >>> a[1:-1] ['eggs', 100] >>> a[:2] + ['bacon', 2*2] ['spam', 'eggs', 'bacon', 4] >>> 3*a[:3] + ['Boe!'] ['spam', 'eggs', 100, 'spam', 'eggs', 100, 'spam', 'eggs', 100, 'Boe!']
??????????????????????????????????????
>>> a ['spam', 'eggs', 100, 1234] >>> a[2] = a[2] + 23 >>> a ['spam', 'eggs', 123, 1234]
??????????????????????????????????С??
>>> # Replace some items: ... a[0:2] = [1, 12] >>> a [1, 12, 123, 1234] >>> # Remove some: ... a[0:2] = [] >>> a [123, 1234] >>> # Insert some: ... a[1:1] = ['bletch', 'xyzzy'] >>> a [123, 'bletch', 'xyzzy', 1234] >>> a[:0] = a # Insert (a copy of) itself at the beginning >>> a [123, 'bletch', 'xyzzy', 1234, 123, 'bletch', 'xyzzy', 1234]
???ú???len()?????????????????
>>> len(a) 8
??????????????????????д?????????????????磺
>>> q = [2, 3] >>> p = [1, q, 4] >>> len(p) 3 >>> p[1] [2, 3] >>> p[1][0] 2 >>> p[1].append('xtra') # See section 5.1 >>> p [1, [2, 3, 'xtra'], 4] >>> q [2, 3, 'xtra']
??????????????p[1]??q????????????????????????????????????
??????????????Python????2??2?????????????磬????????????μ????????????????Fibonacci?????е??????У?
>>> # Fibonacci series: ... # the sum of two elements defines the next ... a, b = 0, 1 >>> while b < 10: ... print b ... a, b = b, a+b ... 1 1 2 3 5 8
????н??????Щ?1????
????а??????????????????a??b????????0??1?????????????????????????????????????????????????????????????????????????
while???????????????????С???Python?У???????C?κη??????棬??????
?????????????????????????????????????κ????????????????????棬??????????????????????????????????????????д????C?????
<
??С?????>
?????????==
?????????<=
??С????????>=????????????!=
???????????
????????????????????Python?????????????? Python?????????????????????????????????????????????tab?????????????? ?????????????????????????????????д???Python?????????????????????????????????????????????????????????????????????б???????????????????3?????????????????У???????????????ж?????????????????????????????顣
print??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
>>> i = 256*256 >>> print 'The value of i is', i The value of i is 65536
print????β??????????????е???У?
>>> a, b = 0, 1 >>> while b < 1000: ... print b, ... a, b = b, a+b ... 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987
????????????????????????д?????????????????????????????????????С?
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?????2. ???Python?????? ?????Python ??? ??? 4. ???????????
Release 2.3, documentation updated on July 29, 2003.
See About this document... for information on suggesting changes. ?????, @ssv
