python 一些基本库 I

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python 一些基本库 I

python 一些基本库 I


1 系统操作 os

    
    >>> import os
    
    
    >>> os.getcwd()      # Return the current working directory
        'C:\\Python37'
    >>> os.chdir('/server/accesslogs')   # Change current working directory
    
    >>> os.system('mkdir today')   # Run the command mkdir in the system shell

2 文件操作 shutils


    >>> import shutil
    >>> shutil.copyfile('data.db', 'archive.db') 拷贝文件
        'archive.db'
    >>> shutil.move('/build/executables', 'installdir') 移动，重命名
        'installdir'

3 查找文件 glob


    import glob
    
    glob.glob("*.go")
    
    ['server.go', 'server1.go']

4 输入输出 sys



1 sys.argv  获取参数

    python demo.py one two
    
    demo.py
    
        import sys
        print(sys.argv)
        >> ['demo.py', 'one', 'two', 'three']


2  sys.stderr

    sys.stderr.write('Warning, log file not found starting a new one\n')
    没有\n 不会输出

5 数学统计相关 math, random, statistic


1 math 
    
    math.cos(math.pi / 4)
    math.log(1024, 2)
    

2 random
    
    random.choice(['apple', 'pear', 'banana'])
    
    random.sample(range(100), 10) # sampling without replacement
    
    random.random()    # random float
    
    random.randrange(6)    # random integer chosen from range(6)


3  statistics

    import statistics
    
    >>> data = [2.75, 1.75, 1.25, 0.25, 0.5, 1.25, 3.5]
    
    >>> statistics.mean(data)
    1.6071428571428572
    
    >>> statistics.median(data)
    1.25
    
    >>> statistics.variance(data)
    1.3720238095238095

6 internet 相关 urllib, smtplib


1  urllib
    
    >>> from urllib.request import urlopen
    >>> with urlopen('http://tycho.usno.navy.mil/cgi-bin/timer.pl') as response:
    ...     for line in response:
    ...         line = line.decode('utf-8')  # Decoding the binary data to text.
    ...         if 'EST' in line or 'EDT' in line:  # look for Eastern Time
    ...             print(line)


2  smtplib

    
    >>> import smtplib
    >>> server = smtplib.SMTP('localhost')
    >>> server.sendmail('soothsayer@example.org', 'jcaesar@example.org',
    ... """To: jcaesar@example.org
    ... From: soothsayer@example.org
    ...
    ... Beware the Ides of March.
    ... """)
    >>> server.quit()

7 时间日期相关 datetime, time

 
from datetime import date

now = date.today()

>>> now #  datetime.date(2003, 12, 2)
   
>>> now.strftime("%m-%d-%y. %d %b %Y is a %A on the %d day of %B.")

  '12-02-03. 02 Dec 2003 is a Tuesday on the 02 day of December.'

>>> birthday = date(1964, 7, 31)
>>> age = now - birthday
>>> age.days
    14368

8 文件压缩 zlib, gzip, bz2, lzma, zipfile, tarfile


    >>> import zlib
    
    >>> s = b'witch which has which witches wrist watch'
    >>> len(s)
    41
    
    >>> t = zlib.compress(s)  压缩
    >>> len(t)
    37
    
    >>> zlib.decompress(t)     解压缩
    b'witch which has which witches wrist watch'
    
    
    >>> zlib.crc32(s)       CRC校验
    226805979

9 性能检测 timeit, profile, pstats

    
    
1 timeit  # Measure execution time of small code snippets


    >>> from timeit import Timer
    
    
    In [17]: Timer("t=a;  a=b; b=t", "a=1; b=2").timeit()
    Out[17]: 0.03515957900003741
    
    In [18]: Timer("a, b= b, a", "a=1; b=2").timeit()
    Out[18]: 0.019163364000064576


2 profile

 import profile

 def test():
    ...:     for i in range(10):
    ...:         print(i*i)

 profile.run("test()", 'test.log' )


  >>> 

   15 function calls in 0.000 seconds

   Ordered by: standard name

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.000    0.000    0.000    0.000 :0(exec)
       10    0.000    0.000    0.000    0.000 :0(print)
        1    0.000    0.000    0.000    0.000 :0(setprofile)
        1    0.000    0.000    0.000    0.000 <ipython-input-19-67b408abaa61>:1(test)
        1    0.000    0.000    0.000    0.000 <string>:1(<module>)
        0    0.000             0.000          profile:0(profiler)
        1    0.000    0.000    0.000    0.000 profile:0(test())



    ●ncalls：表示函数调用的次数；
    
    ●tottime：表示指定函数的总的运行时间，除掉函数中调用子函数的运行时间；
    
    ●percall：（第一个 percall）等于 tottime/ncalls；
    
    ●cumtime：表示该函数及其所有子函数的调用运行的时间，即函数开始调用到返回的时间；
    
    ●percall：（第二个 percall）即函数运行一次的平均时间，等于 cumtime/ncalls；
    
    ●filename:lineno(function)：每个函数调用的具体信息；



3  pstats


    实例化对象

    p = pstats.Stats("test.out")  根据profile之前生成的 分析文件

        # strip_dirs(): 去掉无关的路径信息
        # sort_stats(): 排序，支持的方式和上述的一致
        # print_stats(): 打印分析结果，可以指定打印前几行

    # 按照函数名排序，只打印前3行函数的信息, 参数还可为小数,表示前百分之几的函数信息
        p.strip_dirs().sort_stats("name").print_stats(3)

    # 按照运行时间和函数名进行排序
     p.strip_dirs().sort_stats("cumulative", "name").print_stats(0.8)

    # 如果想知道有哪些函数调用了test
        p.print_callers("test")

    # 查看test()函数中调用了哪些函数
         p.print_callees("test")

10 代码检测 doctest, unittest


1 doctest 

    doctest.txt
        
        >>> from math import gcd
        >>> gcd(3,6)
        3   预期的结果
        >>> gcd(12,6)
        6

          
    
    >> python -m doctest -v doctest.txt   -m 指定模块 -v 表示输出信息
    
        
        Trying:
            from math import gcd
        Expecting nothing
        ok
        Trying:
            gcd(3,6)
        Expecting:
            3
        ok
        Trying:
            gcd(12,6)
        Expecting:
            6
        ok
        1 items passed all tests:
           3 tests in doctest.txt
        3 tests in 1 items.
        3 passed and 0 failed.
        Test passed.



    

2  unittest

    import unittest
    
    
    def average(values):
       ...:     return sum(values) / len(values)
    
    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()  # Calling from the command line invokes all tests
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