Python script to parse 'iwlist scan' into a table

Question

Hi,
I've written a small python script that parses the output of the command "iwlist interface scan" into a table.
Why ?
Like many arch linux users I think, I use netcfg instead of something like network manager or wicd. So the most natural way to scan for wifi networks in range is iwlist scan. But the output of this command is huge and I find it difficult to retrieve information. So this script parses it into a table : one network, one line.
Example output
Name Address Quality Channel Encryption
wifi_1 01:23:45:67:89:AB 100 % 11 WPA v.1
wifi_2 01:23:45:67:89:AC 76 % 11 WEP
wifi_3 01:23:45:67:89:AD 51 % 11 Open
wifi_4 01:23:45:67:89:AE 50 % 11 WPA v.1
wifi_5 01:23:45:67:89:AF 43 % 4 Open
wifi_6 01:23:45:67:89:AG 43 % 4 WPA v.1
Details
It reads from stdin so you use it like that: iwlist wlan0 scan | iwlistparse.py
The width of the columns is determined by what's in it.
You can easily do a bit more than just parsing the info: in the example above, the quality has been calculated to percents from a ratio (e.g. 46/70).
It is sorted, too.
Customization
It's python so it's easy to customize. See the comments in the code.
Code
#!/usr/bin/env python
# iwlistparse.py
# Hugo Chargois - 17 jan. 2010 - v.0.1
# Parses the output of iwlist scan into a table
import sys
# You can add or change the functions to parse the properties of each AP (cell)
# below. They take one argument, the bunch of text describing one cell in iwlist
# scan and return a property of that cell.
def get_name(cell):
return matching_line(cell,"ESSID:")[1:-1]
def get_quality(cell):
quality = matching_line(cell,"Quality=").split()[0].split('/')
return str(int(round(float(quality[0]) / float(quality[1]) * 100))).rjust(3) + " %"
def get_channel(cell):
return matching_line(cell,"Channel:")
def get_encryption(cell):
enc=""
if matching_line(cell,"Encryption key:") == "off":
enc="Open"
else:
for line in cell:
matching = match(line,"IE:")
if matching!=None:
wpa=match(matching,"WPA Version ")
if wpa!=None:
enc="WPA v."+wpa
if enc=="":
enc="WEP"
return enc
def get_address(cell):
return matching_line(cell,"Address: ")
# Here's a dictionary of rules that will be applied to the description of each
# cell. The key will be the name of the column in the table. The value is a
# function defined above.
rules={"Name":get_name,
"Quality":get_quality,
"Channel":get_channel,
"Encryption":get_encryption,
"Address":get_address,
# Here you can choose the way of sorting the table. sortby should be a key of
# the dictionary rules.
def sort_cells(cells):
sortby = "Quality"
reverse = True
cells.sort(None, lambda el:el[sortby], reverse)
# You can choose which columns to display here, and most importantly in what order. Of
# course, they must exist as keys in the dict rules.
columns=["Name","Address","Quality","Channel","Encryption"]
# Below here goes the boring stuff. You shouldn't have to edit anything below
# this point
def matching_line(lines, keyword):
"""Returns the first matching line in a list of lines. See match()"""
for line in lines:
matching=match(line,keyword)
if matching!=None:
return matching
return None
def match(line,keyword):
"""If the first part of line (modulo blanks) matches keyword,
returns the end of that line. Otherwise returns None"""
line=line.lstrip()
length=len(keyword)
if line[:length] == keyword:
return line[length:]
else:
return None
def parse_cell(cell):
"""Applies the rules to the bunch of text describing a cell and returns the
corresponding dictionary"""
parsed_cell={}
for key in rules:
rule=rules[key]
parsed_cell.update({key:rule(cell)})
return parsed_cell
def print_table(table):
widths=map(max,map(lambda l:map(len,l),zip(*table))) #functional magic
justified_table = []
for line in table:
justified_line=[]
for i,el in enumerate(line):
justified_line.append(el.ljust(widths[i]+2))
justified_table.append(justified_line)
for line in justified_table:
for el in line:
print el,
print
def print_cells(cells):
table=[columns]
for cell in cells:
cell_properties=[]
for column in columns:
cell_properties.append(cell[column])
table.append(cell_properties)
print_table(table)
def main():
"""Pretty prints the output of iwlist scan into a table"""
cells=[[]]
parsed_cells=[]
for line in sys.stdin:
cell_line = match(line,"Cell ")
if cell_line != None:
cells.append([])
line = cell_line[-27:]
cells[-1].append(line.rstrip())
cells=cells[1:]
for cell in cells:
parsed_cells.append(parse_cell(cell))
sort_cells(parsed_cells)
print_cells(parsed_cells)
main()
I hope you find it useful. Please report bugs, I haven't tested it a lot. You may have to customize it though, because I think not all iwlist scan outputs are the same. Again, see comments, it should be easy.

Answer 1

This tool is very helpfull. I am trying to add a new function to the existing code to parse the signal level parameter from the output of iwlist wlan0 scan, but I am getting lot of issues .Since I am new to python script can anyone help me to extract the signal level also from the scan put put.
The parametr to be used is Signal level=-44 dBm ,I am trying to create a one more column with Signal level and print its out in the table.
Example:-
Signal level
-44db
The error I am getting
  File "iwlist_parser_Testing.py", line 146, in <module>
    main()
  File "iwlist_parser_Testing.py", line 144, in main
    print_cells(parsed_cells)
  File "iwlist_parser_Testing.py", line 123, in print_cells
    print_table(table)
  File "iwlist_parser_Testing.py", line 102, in print_table
    widths=map(max,map(lambda l:map(len,l),zip(*table))) #functional magic
  File "iwlist_parser_Testing.py", line 102, in <lambda>
    widths=map(max,map(lambda l:map(len,l),zip(*table))) #functional magic
TypeError: object of type 'NoneType' has no len()
Could some pls help me to solve this issue
Thanks