10. 标准库概览

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dir(os)
<返回由模块的所有函数组成的列表>
help(os)
<返回根据模块文档字符串创建的详细说明页面>

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import glob
glob.glob('*.py')
['primes.py', 'random.py', 'quote.py']

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import argparse

parser = argparse.ArgumentParser(
    prog='top',
    description='Show top lines from each file')
parser.add_argument('filenames', nargs='+')
parser.add_argument('-l', '--lines', type=int, default=10)
args = parser.parse_args()
print(args)

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import re
re.findall(r'\bf[a-z]*', 'which foot or hand fell fastest')
['foot', 'fell', 'fastest']
re.sub(r'(\b[a-z]+) \1', r'\1', 'cat in the the hat')
'cat in the hat'

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'tea for too'.replace('too', 'two')
'tea for two'

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from timeit import Timer
Timer('t=a; a=b; b=t', 'a=1; b=2').timeit()
0.57535828626024577
Timer('a,b = b,a', 'a=1; b=2').timeit()
0.54962537085770791

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def average(values):
    """计算数字列表的算术平均值

    >>> print(average([20, 30, 70]))
    40.0
    """
    return sum(values) / len(values)

import doctest
doctest.testmod()   # 自动验证嵌入式测试

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import unittest

class TestStatisticalFunctions(unittest.TestCase):

    def test_average(self):
        self.assertEqual(average([20, 30, 70]), 40.0)
        self.assertEqual(round(average([1, 5, 7]), 1), 4.3)
        with self.assertRaises(ZeroDivisionError):
            average([])
        with self.assertRaises(TypeError):
            average(20, 30, 70)

unittest.main()  # 从命令行调用时会执行所有测试

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from string import Template
t = Template('${village}folk send $$10 to $cause.')
t.substitute(village='Nottingham', cause='the ditch fund')
'Nottinghamfolk send $10 to the ditch fund.'

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import threading, zipfile

class AsyncZip(threading.Thread):
    def __init__(self, infile, outfile):
        super().__init__()
        self.infile = infile
        self.outfile = outfile

    def run(self):
        with zipfile.ZipFile(self.outfile, 'w', zipfile.ZIP_DEFLATED) as f:
            f.write(self.infile)
        print('Finished background zip of:', self.infile)

background = AsyncZip('mydata.txt', 'myarchive.zip')
background.start()
print('The main program continues to run in foreground.')

background.join()    # 等待后台任务结束
print('Main program waited until background was done.')

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import logging
logging.debug('Debugging information')
logging.info('Informational message')
logging.warning('Warning:config file %s not found', 'server.conf')
logging.error('Error occurred')
logging.critical('Critical error -- shutting down')

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from array import array
a = array('H', [4000, 10, 700, 22222])
sum(a)
26932
a[1:3]
array('H', [10, 700])

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from collections import deque
d = deque(["task1", "task2", "task3"])
d.append("task4")
print("Handling", d.popleft())
Handling task1
unsearched = deque([starting_node])
def breadth_first_search(unsearched):
    node = unsearched.popleft()
    for m in gen_moves(node):
        if is_goal(m):
            return m
        unsearched.append(m)

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import bisect
scores = [(100, 'perl'), (200, 'tcl'), (400, 'lua'), (500, 'python')]
bisect.insort(scores, (300, 'ruby'))
scores
[(100, 'perl'), (200, 'tcl'), (300, 'ruby'), (400, 'lua'), (500, 'python')]

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from heapq import heapify, heappop, heappush
data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
heapify(data)                      # 将列表重新调整为堆顺序
heappush(data, -5)                 # 添加一个新条目
[heappop(data) for i in range(3)]  # 获取三个最小的条目
[-5, 0, 1]