Monthly Archives: December 2014

Get required lasts lines from a huge text file in python

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During my work, I need to parse the result from some huge log files. The result is always save at the end of the file. So I need find a way to get the required last lines to accelerate the parse speed. Here is the function I have written to achieve this requirement in python.

  1. def last_lines(filename, lines=1):
  2.     '''
  3.     return the last lines from the specify files
  4.     '''
  5.     with open(filename, 'rb') as fh:
  6.         fh.seek(0, os.SEEK_END)
  7.         if fh.tell() == 0:
  8.             return []
  9.         fh.seek(-2, os.SEEK_END)
  10.         #while not BOF
  11.         while fh.tell() > 0:
  12.             cur_char = fh.read(1).decode()
  13.             if cur_char == '\n':
  14.                 lines -= 1
  15.             if lines > 0:
  16.                 fh.seek(-2, os.SEEK_CUR)
  17.             else:
  18.                 break
  19.         return [line.decode() for line in fh.readlines()]

 

Use oscilloscope Check the AC noise of a Power Source

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How to use a oscilloscope display the wave shape of AC power source?
1. Check the oscilloscope is connected with attenuator probes, and adjust to the right attenuation factor. 1x, 10x 100x, … the more big the number the more attenuator value

2. Adjust the oscilloscope to the relative measure scope and set to the right channel

3. Connect the ground with the clamp to the ground of the source
10092166

4. Use one probe connecting with zero line, the other connected with the supply line

5. Adjust the sample time to make the wave shape looks better

6. The noise pulses are displayed during my measurement result

WP_20141212_14_13_43_Pro

WP_20141212_14_10_58_Pro

Use Python puka client with RabbitMQ

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Send a message to RabbitMQ

  1. #!/usr/bin/env python
  2.  
  3. import sys
  4. sys.path.append("..")
  5.  
  6.  
  7. import puka
  8.  
  9. client = puka.Client("amqp://localhost/")
  10.  
  11. promise = client.connect()
  12. client.wait(promise)
  13.  
  14. promise = client.queue_declare(queue='test')
  15. client.wait(promise)
  16.  
  17. promise = client.basic_publish(exchange='', routing_key='test',
  18.                               body="Hello world!")
  19. client.wait(promise)
  20.  
  21. print " [*] Message sent"
  22.  
  23. promise = client.queue_declare(queue='test', passive=True)
  24. print " [*] Queue size:", client.wait(promise)['message_count']
  25.  
  26. promise = client.close()
  27. client.wait(promise)

Setup WordPress Site in Ubuntu

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To install wordpress in Ubuntu Server, a few steps are required:

1. Update your system by

# apt-get update
# apt-get upgrade

2. install apache2

# apt-get apache2

3. install MySQL

# apt-get mysql

4. install WordPress

# apt-get wordpress

5. Configure WordPress in ubuntu

6. Configure your wordpress site to support it access from the root of url

7. install ftp to your server to support wordpress install plugin

# apt-get ftp

8. if encounter a error, “can’t create directory”, when install a plugin from admin panel, check this link to change the configuration to fix it