Chrome Downloads Bar Hide or Disable

Chrome downloads bar is probably the worst 'liked' feature about Google Chrome according to discussions in Google Products Forum. And rightly so. Like so many others, I too hate it. The dislike gets intensified since Chrome provides no easy option to hide or disable the bar. After a long search, I finally discovered one option to achieve this: Go to 'chrome://flags/' and disable the 'New Downloads UI'. A relaunch is required and wohoo the download bar hides nicely.


Now, the sad part. The page at 'chrome://flags/' mentions that the experiments may bite and they are serious about it! :( 


If you try to download a file that is an installer i.e. a dmg/exe file or even part of an extension, chrome asks for a confirmation. With the downloads bar now hidden,  the option to ask a confirmation remains hidden and thus you're hanging in the balance. The download remains stuck and at some point you must revert back to enable the 'New Downloads UI' to carry on with life :( Ahh.. Google.. Please give us the option!

pipe with rm

I wanted to delete a large number of files in a directory that satisfied a certain criteria in their name.  The command for this is:


find /path/to/dir -name '*criteria*' -exec rm {} \;

or



find /path/to/dir -name '*criteria*'| xargs rm

or


ls | grep criteria | xargs rm

Note: The last command might be slower than the first two.

Plotting a random geometric graph using Networkx

I wanted to plot the random geometric graph as shown in networkx gallery with a few tweaks. I wanted to have two plots: 1) A plot of 600 nodes with nodes in only one color and 2) A similar plot of 600 nodes with few (75) nodes highlighted with a different color. I thought it would be an easy process if I download the code and update the code with a few additional lines to perform my work. Unfortunately, when I downloaded the code and executed it (without any changes), the code crashed on the second line with the following error codes:

Traceback (most recent call last):
  File "random_geometric_graph.py", line 6, in <module>
    pos=nx.get_node_attributes(G,'pos')
AttributeError: 'module' object has no attribute 'get_node_attributes'

I checked to see if I had the latest versions of NetworkX and Matplotlib and I did. No idea why a piece of code downloaded directly from the library's official website won't run. To be sure something wasn't wrong in the way libraries were linked in my machine, I decided to recheck the code on another machine . Same error and same crash.. No idea. Finally I decided to check the code in the library itself. Everything with get_node_attributes function seemed to be okay so I copied it to my working file and it failed again! Narrowing down, it looked like the code had problem accessing the node elements and thus the function crashed. Fast forward, I decided to copy the graph generation function and return the attributes simultaneously to a different variable. Here is my final code:

---

# -*- coding: utf-8 -*-
"""
Generators for geometric graphs.
"""
#    Copyright (C) 2004-2011 by 
#    Aric Hagberg <hagberg@lanl.gov>
#    Dan Schult <dschult@colgate.edu>
#    Pieter Swart <swart@lanl.gov>
#    All rights reserved.
#    BSD license.
from __future__ import print_function

__author__ = "\n".join(['Aric Hagberg (hagberg@lanl.gov)',
                        'Dan Schult (dschult@colgate.edu)',
                        'Ben Edwards (BJEdwards@gmail.com)'])

__all__ = ['random_geometric_graph',
           'waxman_graph',
           'geographical_threshold_graph',
           'navigable_small_world_graph']
from bisect import bisect_leftfrom functools import reducefrom itertools import productimport math, random, sysimport networkx as nx
import matplotlib.pyplot as plt
#---------------------------------------------------------------
#  Random Geometric Graphs
#---------------------------------------------------------------
        def random_geometric_graph(n, radius, dim=2, pos=None):
    r"""Return the random geometric graph in the unit cube.

    The random geometric graph model places n nodes uniformly at random 
    in the unit cube  Two nodes `u,v` are connected with an edge if
    `d(u,v)<=r` where `d` is the Euclidean distance and `r` is a radius 
    threshold.

    Parameters
    ----------
    n : int
        Number of nodes
    radius: float
        Distance threshold value  
    dim : int, optional
        Dimension of graph
    pos : dict, optional
        A dictionary keyed by node with node positions as values.

    Returns
    -------
    Graph
      
    Examples
    --------
    >>> G = nx.random_geometric_graph(20,0.1)

    """
    G=nx.Graph()
    G.name="Random Geometric Graph"
    G.add_nodes_from(range(n)) 
    if pos is None:
        # random positions 
        for n in G:
            G.node[n]['pos']=[random.random() for i in range(0,dim)]
    else:
        nx.set_node_attributes(G,'pos',pos)
    
 
    name = 'pos'
    position_data = dict( (n,d[name]) for n,d in G.node.items() if name in d)
    
    # connect nodes within "radius" of each other
    # n^2 algorithm, could use a k-d tree implementation
    nodes = G.nodes(data=True)
    while nodes:
        u,du = nodes.pop()
        pu = du['pos']
        for v,dv in nodes:
            pv = dv['pos']
            d = sum(((a-b)**2 for a,b in zip(pu,pv)))
            if d <= radius**2:
                G.add_edge(u,v)
                
    return G,position_data


n = 600
d = 0.0725


G,pos = random_geometric_graph(n,d)
print(n,'t',G.number_of_edges())
# find node near center (0.5,0.5)
dmin=1
ncenter=0
for n in pos:
    x,y=pos[n]
    d=(x-0.5)**2+(y-0.5)**2
    if d<dmin:
        ncenter=n
        dmin=d

# color by path length from node near center
#p=nx.single_source_shortest_path_length(G,ncenter)

highlighted_nodes = random.sample(xrange(n),75)
#print(highlighted_nodes)
p = {}

base_color = '#0F1C95'
trust_color = '#36D258'
for i in range(n+1):
        p[i] = base_color
        if i in highlighted_nodes:
                p[i] = trust_color

plt.figure(figsize=(9,9))
nx.draw_networkx_edges(G,pos,nodelist=[ncenter],alpha=0.4)
nx.draw_networkx_nodes(G,pos,nodelist=p.keys(),node_size=100,node_color=p.values(),cmap=plt.cm.Reds_r)

plt.xlim(-0.05,1.05)
plt.ylim(-0.05,1.05)
plt.axis('off')
plt.savefig('highlighted_graph.png')

plt.xlim(-0.05,1.05)
plt.ylim(-0.05,1.05)
plt.axis('off')
nx.draw_networkx_nodes(G,pos,nodelist=p.keys(),node_size=100,node_color=base_color,cmap=plt.cm.Reds_r)
plt.savefig('no-highlight_graph.png')

---

Reading unicode data through Python

Processing files containing unicode based characters requires using the codec library instead of the standard file processing libraries. The relevant code:

import codecs

file = codecs.open("file_with_unicode_data.txt", "r", "utf-8")
print file.readlines()
file.close()

Difference between two folders

Redirect output of difference between two directories, removing the system files (DS_Store, etc..):

diff -qr dir1 dir2 | grep -v -e 'DS_Store' -e 'Thumbs' | sort > diffs_dir1_dir2.txt

Specify the location with Wget?

-P prefix
--directory-prefix=prefix
           Set directory prefix to prefix.  The directory prefix is the
           directory where all other files and sub-directories will be
           saved to, i.e. the top of the retrieval tree.  The default
           is . (the current directory).

wget -P /home/username/location URL

Add a column to an existing MySQL table

To add a column called new_column to a table called table_name with a datatype of VARCHAR(20), use the following SQL statement:

ALTER TABLE table_name ADD new_column VARCHAR(20);

This statement will add the new column new_column to the end of the table. To insert the new column after a specific column, such as old_column, use this statement:

ALTER TABLE table_name ADD new_column VARCHAR(20) AFTER old_column;

To add the new column as the first column, we can use the following mysql statement:

ALTER TABLE table_name ADD new_column VARCHAR(60) FIRST;