I have a working code to print random lines from a csv column.
#!/usr/bin/python
import csv
from random import shuffle
filename = 'example.csv'
col = 2
sample = 100
with open(filename, 'r') as f:
reader = csv.reader(f)
data = [row[col] for row in reader]
shuffle(data)
print '\n'.join(data[:sample])
How can I parameterize this script by passing filename, col & sample (e.g. 100 values)?
You can use the sys module like this to pass command line arguments to your Python script.
import sys
name_of_script = sys.argv[0]
position = sys.argv[1]
sample = sys.argv[2]
and then your command line would be:
./myscript.py 10 100
Use argparse module:
The argparse module makes it easy to write user-friendly command-line interfaces. The program defines what arguments it requires, and argparse will figure out how to parse those out of sys.argv. The argparse module also automatically generates help and usage messages and issues errors when users give the program invalid arguments.
It's pretty powerful: you can specify help messages, make validations, provide defaults..whatever you can imagine about working with command-line arguments.
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("-p", "--position", type=int)
parser.add_argument("-s", "--sample", type=int)
args = parser.parse_args()
col = args.position
sample = args.sample
print col
print sample
Here's what on the command-line:
$ python test.py --help
usage: test.py [-h] [-p POSITION] [-s SAMPLE]
optional arguments:
-h, --help show this help message and exit
-p POSITION, --position POSITION
-s SAMPLE, --sample SAMPLE
$ python test.py -p 10 -s 100
10
100
$ python test.py --position 10 --sample 100
10
100
Speaking about the code you've provided:
import random statementfrom random import shuffle to the top of the scriptf.close() (especially with ;) - with handles closing the file automagicallyHere's how the code would look like after the fixes:
#!/usr/bin/python
import argparse
import csv
from random import shuffle
parser = argparse.ArgumentParser()
parser.add_argument("-p", "--position", type=int)
parser.add_argument("-s", "--sample", type=int)
args = parser.parse_args()
with open('<filename>', 'r') as f:
reader = csv.reader(f)
data = [row[args.position] for row in reader]
shuffle(data)
print '\n'.join(data[:args.sample])
I could not install argparse due to lack of permission - meanwhile.
Here's the solution:
#!/usr/bin/python
import csv # This will help us reading csv formated files.
import sys
import optparse #import optparse
from random import shuffle
parser=optparse.OptionParser()
# import options
parser.add_option('-f','--filename',help='Pass the csv filename')
parser.add_option('-p','--position',help='column position in the file',type=int)
parser.add_option('-s','--sample',help='sample size',type=int)
(opts,args) = parser.parse_args() # instantiate parser
# Program to select random values
with open('<filepath>'+opts.filename,'r') as f:
reader=csv.reader(f)
data=[row[opts.position] for row in reader]
shuffle(data)
#print '\n'.join(data[:opts.sample])
# create o/p file
file=open("<opfilename>.txt","w")
file.write('\n'.join(data[:opts.sample]))
file.close()
