Python读取实时数据流示例

Python  /  管理员 发布于 7年前   143

1、#coding:utf-8

chose = [  ('foo',1,2),  ('bar','hello'),  ('foo',3,4)]def do_foo(x,y):  print('foo',x,y)def do_bar(s):  print('bar',s)for tag,*args in chose:  if tag == 'foo':    do_foo(*args)  elif tag == 'bar':    do_bar(*args)line = 'nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false'uname,*fields,homedir,sh = line.split(':')print(sh)from collections import dequedef search(lines, pattern, history=5):  previous_lines = deque(maxlen=history)  for li in lines:    if pattern in li:      yield li, previous_lines    previous_lines.append(li)# Example use on a fileif __name__ == '__main__':  with open(r'./somefiles.py') as f:    for line, prevlines in search(f, 'python', 5):      for pline in prevlines:        print(pline, end='')      print(line, end='')      print('-' * 20)

2、import heapq

portfolio = [{'name': 'IBM', 'shares': 100, 'price': 91.1},{'name': 'AAPL', 'shares': 50, 'price': 543.22},{'name': 'FB', 'shares': 200, 'price': 21.09},{'name': 'HPQ', 'shares': 35, 'price': 31.75},{'name': 'YHOO', 'shares': 45, 'price': 16.35},{'name': 'ACME', 'shares': 75, 'price': 115.65}]cheap = heapq.nsmallest(3, portfolio, key=lambda s: s['price'])expensive = heapq.nlargest(3, portfolio, key=lambda s: s['price'])print(cheap)print(expensive)

3、读取流数据源

如果数据是来自一个连续的数据源，我们需要读取连续数据，接下来

我们介绍一个适用于许多真是场景的简单解决方案，然而它并不是通用的。

操作步骤：

在本节中我们将想你演示如何读取一个实时变化的文件，并把输入打印出来。

import timeimport osimport sysif len(sys.argv) != 2:  print('>>sys.stderr,"请输入需要读取的文件名！"')filename = sys.argv[1]if not os.path.isfile(filename):  print('>>sys.stderr,"请给出需要的文件：\%s\: is not a file" % filename')with open(filename,'r') as f:  filesize = os.stat(filename)[6]  f.seek(filesize)  while True:    where = f.tell()    line = f.readline()    if not line:      time.sleep(1)      f.seek(where)    else:      print(line)

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