本文将讲解Python标准库内容,有操作系统接口os、文件路径通配符glob、命令行参数sys、正则表达式re、数学math、日期与时间、数据压缩、性能评估等,我们只需要知道有些什么内容,用到时候再查找资料即可,无需熟记,也记不住。
1-路径操作
import os
os.getcwd()#获取当前路径
os.chdir('../')#改变当前路径
os.getcwd()#获取当前路径
2-不同操作系统有不同接口函数
有进程参数、文件创建、进程管理、调度等
具体参考:https://docs.python.org/3.6/library/os.html#module-os
3-文件通配符
import glob
glob.glob('*.py')#返回当前路径下所有py文件数组
适配查找文件
>>> import glob
>>> glob.glob('./[0-9].*')
['./1.gif', './2.txt']
>>> glob.glob('*.gif')
['1.gif', 'card.gif']
>>> glob.glob('?.gif')
['1.gif']
>>> glob.glob('**/*.txt', recursive=True)
['2.txt', 'sub/3.txt']
>>> glob.glob('./**/', recursive=True)
['./', './sub/']
4-命令行参数
参考:https://docs.python.org/3.6/library/sys.html#module-sys
1-示例
>>> import re
>>> re.findall(r'bf[a-z]*', 'which foot or hand fell fastest')
#b表示匹配一个单词边界,也就是指单词和空格间的位置。 f开始的单词
['foot', 'fell', 'fastest']
>>> re.sub(r'(b[a-z]+) 1', r'1', 'cat in the the hat')
'cat in the hat'
2-正则表达式语法
re.match(pattern, string, flags=0)
更多参考:https://docs.python.org/3.6/library/re.html#module-re
1-math
涵括:数论计算、指数计算、三角函数、角度计算、双曲线、常量等
直接传入参数调用函数即可,比较简单,请参考:https://docs.python.org/3.6/library/math.html#module-math
import math
math.gamma(0.5)#伽马函数
math.pi#Π值
2-datetime
>>> # dates are easily constructed and formatted
>>> 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.'
>>> # dates support calendar arithmetic
>>> birthday = date(1964, 7, 31)
>>> age = now - birthday
>>> age.days
14368
常见数据压缩格式: zlib, gzip, bz2, lzma, zipfile and tarfile.
>>> import zlib
>>> s = b'witch which has which witches wrist watch'
>>> len(s)
41
>>> t = zlib.compress(s)
>>> len(t)
37
>>> zlib.decompress(t)
b'witch which has which witches wrist watch'
>>> zlib.crc32(s)
226805979
模块:
import threading
import time
exitFlag = 0
class myThread (threading.Thread):
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self):
print ("开始线程:" + self.name)
print_time(self.name, self.counter, 5)
print ("退出线程:" + self.name)
def print_time(threadName, delay, counter):
while counter:
if exitFlag:
threadName.exit()
time.sleep(delay)
print ("%s: %s" % (threadName, time.ctime(time.time())))
counter -= 1
# 创建新线程
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
# 开启新线程
thread1.start()
thread2.start()
thread1.join()
thread2.join()
print ("退出主线程")
Thread 对象的 Lock 和 Rlock 可以实现简单的线程同步,Python 的 Queue 模块中提供了同步的、线程安全的队列类,包括FIFO(先入先出)队列Queue,LIFO(后入先出)队列LifoQueue,和优先级队列 PriorityQueue。更多参考:https://www.runoob.com/python3/python3-multithreading.html
为了提高性能,采用弱引用方式调用对象,当删除对象的时候,自动释放内存,引用失效。常用于创建对象耗时、缓存对象等。
>>> import weakref, gc
>>> class A:
... def __init__(self, value):
... self.value = value
... def __repr__(self):
... return str(self.value)
...
>>> a = A(10) # create a reference
>>> d = weakref.WeakValueDictionary()
>>> d['primary'] = a # does not create a reference
>>> d['primary'] # fetch the object if it is still alive
10
>>> del a # remove the one reference
>>> gc.collect() # run garbage collection right away
0
>>> d['primary'] # entry was automatically removed
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
d['primary'] # entry was automatically removed
File "C:/python36/lib/weakref.py", line 46, in __getitem__
o = self.data[key]()
KeyError: 'primary'
还有logging日志,array、collections数组集合工具、decimal浮点数运算、reprlib输出格式等等