Pickling: How to serialize objects

There is an example on how to serialize and de-serialize python objects.

import pickle
import random

print 'Write data...'
output = open('mydata.pkl', 'wb')
for i in range(0,5): # writing five lists on the file
 list = random.sample(range(0,100),10) # random integers list
 print 'saving:',list
 pickle.dump(list, output)
output.close()

print 'Load data...'
input = open("mydata.pkl","rb") # open the file in reading mode
try:
 while True: # load from the file until EOF is reached
  list = pickle.load(input)
  print 'loaded: ',list
except EOFError:
  print 'End of file reached'
input.close()

This is the output:

Write data...
saving: [15, 10, 85, 65, 17, 31, 19, 2, 68, 44]
saving: [96, 2, 27, 90, 99, 66, 31, 97, 51, 12]
saving: [82, 61, 12, 49, 50, 84, 91, 83, 23, 89]
saving: [83, 28, 85, 75, 14, 68, 96, 58, 5, 66]
saving: [55, 73, 1, 24, 29, 92, 58, 96, 41, 10]
Load data...
loaded:  [15, 10, 85, 65, 17, 31, 19, 2, 68, 44]
loaded:  [96, 2, 27, 90, 99, 66, 31, 97, 51, 12]
loaded:  [82, 61, 12, 49, 50, 84, 91, 83, 23, 89]
loaded:  [83, 28, 85, 75, 14, 68, 96, 58, 5, 66]
loaded:  [55, 73, 1, 24, 29, 92, 58, 96, 41, 10]
End of file reached

How to create a chart with Google Chart API

The example shows how to create a scatter plot using the Google Chart API.

import random
import urllib

def list2String(x):
 """ from a list like [1,2,5]
     return a string like '1,2,5' """
 data = ""
 for i in x:
  data += str(i)+","
 return data[0:len(data)-1]

def makeChart(x,y,filename):
 query_url = "http://chart.apis.google.com/chart?chxt=x,y&chs=300x200&cht=s&chd=t:"
 query_url += list2String(x)+"|"+list2String(y)
 chart = urllib.urlopen(query_url) # retrieve the chart
 print "saving",query_url
 f = open(filename,"wb")
 f.write(chart.read()) # save the pic
 f.close()

x = random.sample(range(0,100),10) # list with
y = random.sample(range(0,100),10) # random values in [0 100[
makeChart(x,y,"chart.png")

You can embed the picture in a web page:

<img alt="Google chart example" src="http://chart.apis.google.com/chart?chxt=x,y&amp;chs=300x200&amp;cht=s&amp;chd=t:64,10,18,42,49,83,73,27,44,51|77,89,13,87,27,34,38,44,22,42" />

Or use it from the disk.

How to delete all the files in a directory

import os

dirPath = "/home/giu/pyExperiments/toRemove"
fileList = os.listdir(dirPath)
for fileName in fileList:
 os.remove(dirPath+"/"+fileName)

How to list files in a directory

This code will print the content of the directory "/home/giu/Documents/secrets"

import os

fileList = os.listdir("/home/giu/Documents/secrets")
for fileName in fileList:
 print fileName

howtoconquertheworld.pdf
hellokitty.jpg
loveletter.txt
misterious_pictures