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>>> s = '深入 Python' ①
>>> len(s) ②
9
>>> s[0] ③
'深'
>>> s + ' 3' ④
'深入 Python 3'
- ① . Python ('), (").
- ② len() , .. . , , . .
- ③ , , .
- ④ , , +.
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, .
humansize.py:
SUFFIXES = {1000: ['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'], ①
1024: ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']}
def approximate_size(size, a_kilobyte_is_1024_bytes=True):
'''Convert a file size to human-readable form. ②
Keyword arguments:
size -- file size in bytes
a_kilobyte_is_1024_bytes -- if True (default), use multiples of 1024
if False, use multiples of 1000
Returns: string
''' ③
if size < 0:
raise ValueError('number must be non-negative') ④
multiple = 1024 if a_kilobyte_is_1024_bytes else 1000
for suffix in SUFFIXES[multiple]:
size /= multiple
if size < multiple:
return '{0:.1f} {1}'.format(size, suffix) ⑤
raise ValueError('number too large')
- ① 'KB', 'MB', 'GB' - .
- ② - . , .
- ③ .
- ④ , .
- ⑤ , ?
Python 3 . . - .
>>> username = 'mark'
>>> password = 'PapayaWhip' ①
>>> "{0}'s password is {1}".format(username, password) ②
"mark's password is PapayaWhip"
- ① , PapayaWhip
- ② . , format() . - , . , . , {0} {1} , , format()
: . format(). , {0} ( username), {1} (password), &c. , format(). . , .
>>> import humansize
>>> si_suffixes = humansize.SUFFIXES[1000] ①
>>> si_suffixes
['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']
>>> '1000{0[0]} = 1{0[1]}'.format(si_suffixes) ②
'1000KB = 1MB'
- ① , - humansize, , : ( 1000)
- ② , . {0} , format() ( si_suffixes). si_suffixes - . {0[0]} : 'KB'. {0[1]} : 'MB'. , - 1000, , - . '1000KB = 1MB'.
{0} is replaced by the 1st format() argument. {1} is replaced by the 2nd.
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>>> import humansize
>>> import sys
>>> '1MB = 1000{0.modules[humansize].SUFFIXES[1000][0]}'.format(sys)
'1MB = 1000KB'
:
sys Python. , format(). {0} sys. sys.modules , Python. - ; - , . {0.modules} . sys.modules['humansize'] - , humansize, . {0.modules[humansize]} humansize. , . Python sys.modules , ( 'humansize'). PEP 3101: : " . , . - ". sys.modules['humansize'].SUFFIXES - , humansize. {0.modules[humansize].SUFFIXES} .
sys.modules['humansize'].SUFFIXES[1000] - : ['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']. {0.modules[humansize].SUFFIXES[1000]} . sys.modules['humansize'].SUFFIXES[1000][0] - : 'KB'. {0.modules[humansize].SUFFIXES[1000][0]} KB.
! -. humansize.py:
if size < multiple:
return '{0:.1f} {1}'.format(size, suffix)
{1} format(), suffix. {0:.1f}? : {0}, :.1f, . ( ) , .
☞ , printf() C. , , 16- .
(:) . ".1" " " ( ). "f" " " (f ixed-point number) ( - ). size 698.24 suffix - 'GB', '698.2 GB', 698.24 , .
>>> '{0:.1f} {1}'.format(698.24, 'GB')
'698.2 GB'
"Format Specification Mini-Language" Python 3.
.
>>> s = '''Finished files are the re- ①
... sult of years of scientif-
... ic study combined with the
... experience of years.'''
>>> s.splitlines() ②
['Finished files are the re-',
'sult of years of scientif-',
'ic study combined with the',
'experience of years.']
>>> print(s.lower()) ③
finished files are the re-
sult of years of scientif-
ic study combined with the
experience of years.
>>> s.lower().count('f') ④
6
- ① Python . . ENTER . . ENTER Python ( s).
- ② splitlines() , . , .
- ③ lower() . ( upper() .)
- ④ count() . , 6 "f".
. - key1=value1&key2=value2, {key1: value1, key2: value2}.
>>> query = 'user=pilgrim&database=master&password=PapayaWhip'
>>> a_list = query.split('&') ①
>>> a_list
['user=pilgrim', 'database=master', 'password=PapayaWhip']
>>> a_list_of_lists = [v.split('=', 1) for v in a_list] ②
>>> a_list_of_lists
[['user', 'pilgrim'], ['database', 'master'], ['password', 'PapayaWhip']]
>>> a_dict = dict(a_list_of_lists) ③
>>> a_dict
{'password': 'PapayaWhip', 'user': 'pilgrim', 'database': 'master'}
- ① split() , , . (&), .
- ② , , = . = : . ( . 'key=value=foo'.split('=')), ['key', 'value', 'foo'].)
- ③ Python dict().
☞ URL, . URL, urllib.parse.parse_qs(), .
, . . , , .
>>> a_string = 'My alphabet starts where your alphabet ends.'
>>> a_string[3:11] ①
'alphabet'
>>> a_string[3:-3] ②
'alphabet starts where your alphabet en'
>>> a_string[0:2] ③
'My'
>>> a_string[:18] ④
'My alphabet starts'
>>> a_string[18:] ⑤
' where your alphabet ends.'
- ① , "", . , , .
- ② , .
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- ④ 0, . a_string[:18] - , a_string[0:18].
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