“应知应会”的Python功能及特性
翻译：鄂世嘉, Garfielt, Rhys
链接：oschina.net/translate/python-functions
00.带任意数量参数的函数
def function(arg1="", arg2=""):
print "arg1: {0}".format(arg1)
print "arg2: {0}".format(arg2)
function("Hello", "World")
# prints args1: Hello
# prints args2: World
function()
# prints args1:
# prints args2:
def foo(*args):
# just use "*" to collect all remaining arguments into a tuple
numargs = len(args)
print "Number of arguments: {0}".format(numargs)
for i, x in enumerate(args):
print "Argument {0} is: {1}".format(i, x)
foo()
# Number of arguments: 0
foo("hello")
# Number of arguments: 1
# Argument 0 is: hello
foo("hello", "World", "Again")
# Number of arguments: 3
# Argument 0 is: hello
# Argument 1 is: World
# Argument 2 is: Again
01.使用Glob()查找文件
它像是一个更强大版本的listdir()函数。它可以让你通过使用模式匹配来搜索文件。
import glob
# get all py files
files = glob.glob('*.py')
print files
# Output
# ['arg.py', 'g.py', 'shut.py', 'test.py']
import itertools as it, glob
def multiple_file_types(*patterns):
return it.chain.from_iterable(glob.glob(pattern) \
for pattern in patterns)
for filename in multiple_file_types("*.txt", "*.py"):
# add as many filetype arguements
print filename
# output
# =========#
# test.txt
# arg.py
# g.py
# shut.py
# test.py
import itertools as it, glob, os
def multiple_file_types(*patterns):
return it.chain.from_iterable(glob.glob(pattern) \
for pattern in patterns)
for filename in multiple_file_types("*.txt", "*.py"):
# add as many filetype arguements
realpath = os.path.realpath(filename)
print realpath
# output
#=========#
# C:\xxx\pyfunc\test.txt
# C:\xxx\pyfunc\arg.py
# C:\xxx\pyfunc\g.py
# C:\xxx\pyfunc\shut.py
# C:\xxx\pyfunc\test.py
02.调试
import logging, inspect
logging.basicConfig(level=logging.INFO,
format='%(asctime)s %(levelname)-8s %(filename)s:%(lineno)-4d: %(message)s',
datefmt='%m-%d %H:%M',
)
logging.debug('A debug message')
logging.info('Some information')
logging.warning('A shot across the bow')
def test():
frame, filename, line_number, function_name, lines, index = \
inspect.getouterframes(inspect.currentframe())[1]
print(frame, filename, line_number, function_name, lines, index)
test()
# Should print the following (with current date/time of course)
# 10-19 19:57 INFO test.py:9 : Some information
# 10-19 19:57 WARNING test.py:10 : A shot across the bow
# (, 'C:/xxx/pyfunc/magic.py', 16, '', ['test()\n'], 0)
03.生成唯一ID
其实有一个名为uuid()的Python函数是用于这个目的的。
import uuid
result = uuid.uuid1()
print result
# output => various attempts
# 9e177ec0-65b6-11e3-b2d0-e4d53dfcf61b
# be57b880-65b6-11e3-a04d-e4d53dfcf61b
# c3b2b90f-65b6-11e3-8c86-e4d53dfcf61b
import hmac, hashlib
key = '1'
data = 'a'
print hmac.new(key, data, hashlib.sha256).hexdigest()
m = hashlib.sha1()
m.update("The quick brown fox jumps over the lazy dog")
print m.hexdigest()
# c6e693d0b35805080632bc2469e1154a8d1072a86557778c27a01329630f8917
# 2fd4e1c67a2d28fced849ee1bb76e7391b93eb12
04.序列化
import pickle
variable = ['hello', 42, [1, 'two'], 'apple']
# serialize content
file = open('serial.txt', 'w')
serialized_obj = pickle.dumps(variable)
file.write(serialized_obj)
file.close()
# unserialize to produce original content
target = open('serial.txt', 'r')
myObj = pickle.load(target)
print serialized_obj
print myObj
# output
# (lp0
# S'hello'
# p1
# aI42
# a(lp2
# I1
# aS'two'
# p3
# aaS'apple'
# p4
# a.
# ['hello', 42, [1, 'two'], 'apple']
import json
variable = ['hello', 42, [1, 'two'], 'apple']
print "Original {0} - {1}".format(variable, type(variable))
# encoding
encode = json.dumps(variable)
print "Encoded {0} - {1}".format(encode, type(encode))
# deccoding
decoded = json.loads(encode)
print "Decoded {0} - {1}".format(decoded, type(decoded))
# output
# Original ['hello', 42, [1, 'two'], 'apple'] -
# Encoded ["hello", 42, [1, "two"], "apple"] -
# Decoded [u'hello', 42, [1, u'two'], u'apple'] -
05.压缩字符
import zlib
string = """ Lorem ipsum dolor sit amet, consectetur
adipiscing elit. Nunc ut elit id mi ultricies
adipiscing. Nulla facilisi. Praesent pulvinar,
sapien vel feugiat vestibulum, nulla dui pretium orci,
non ultricies elit lacus quis ante. Lorem ipsum dolor
sit amet, consectetur adipiscing elit. Aliquam
pretium ullamcorper urna quis iaculis. Etiam ac massa
sed turpis tempor luctus. Curabitur sed nibh eu elit
mollis congue. Praesent ipsum diam, consectetur vitae
ornare a, aliquam a nunc. In id magna pellentesque
tellus posuere adipiscing. Sed non mi metus, at lacinia
augue. Sed magna nisi, ornare in mollis in, mollis
sed nunc. Etiam at justo in leo congue mollis.
Nullam in neque eget metus hendrerit scelerisque
eu non enim. Ut malesuada lacus eu nulla bibendum
id euismod urna sodales. """
print "Original Size: {0}".format(len(string))
compressed = zlib.compress(string)
print "Compressed Size: {0}".format(len(compressed))
decompressed = zlib.decompress(compressed)
print "Decompressed Size: {0}".format(len(decompressed))
# output
# Original Size: 1022
# Compressed Size: 423
# Decompressed Size: 1022
06.注册Shutdown函数
import atexit
import time
import math
def microtime(get_as_float=False):
if get_as_float:
return time.time()
else:
return '%f %d' % math.modf(time.time())
start_time = microtime(False)
atexit.register(start_time)
def shutdown():
global start_time
print "Execution took: {0} seconds".format(start_time)
atexit.register(shutdown)
# Execution took: 0.297000 1387135607 seconds
# Error in atexit._run_exitfuncs:
# Traceback (most recent call last):
# File "C:\Python27\lib\atexit.py", line 24, in _run_exitfuncs
# func(*targs, **kargs)
# TypeError: 'str' object is not callable
# Error in sys.exitfunc:
# Traceback (most recent call last):
# File "C:\Python27\lib\atexit.py", line 24, in _run_exitfuncs
# func(*targs, **kargs)
# TypeError: 'str' object is not callable
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