Python读取实时数据流示例

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 deque
def 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 file
if __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)

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)

import time
import os
import sys

if 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)