Question

here’s the code!

import csv

def do_work():
      global data
      global b
      get_file()
      samples_subset1()
      return

def get_file():

      start_file='thefile.csv'

      with open(start_file, 'rb') as f:
        data = list(csv.reader(f))
        import collections
        counter = collections.defaultdict(int)

      for row in data:
        counter[row[10]] += 1
      return

def samples_subset1():

      with open('/pythonwork/samples_subset1.csv', 'wb') as outfile:
          writer = csv.writer(outfile)
          sample_cutoff=5000
          b_counter=0
          global b
          b=[]
          for row in data:
              if counter[row[10]] >= sample_cutoff:
                 global b
                 b.append(row) 
                 writer.writerow(row)
                 #print b[b_counter]
                 b_counter+=1
      return

i am a beginner at python. the way my code runs is i call do_work and do_Work will call the other functions. here are my questions:

1. if i need datato be seen by only 2 functions should i make it global? if not then how should i call samples_subset1? should i call it from get_file or from do_work?

2. the code works but can you please point other good/bad things about the way it is written?

3. i am processing a csv file and there are multiple steps. i am breaking down the steps into different functions like get_file, samples_subset1, and there are more that i will add. should i continue to do it the way i am doing it right now here i call each individual function from do_work?

here is the new code, according to one of the answers below:

import csv
import collections

def do_work():
      global b
      (data,counter)=get_file('thefile.csv')
      samples_subset1(data, counter,'/pythonwork/samples_subset1.csv')
      return

def get_file(start_file):

        with open(start_file, 'rb') as f:
        global data
        data = list(csv.reader(f))
        counter = collections.defaultdict(int)

      for row in data:
        counter[row[10]] += 1
      return (data,counter)

def samples_subset1(data,counter,output_file):

      with open(output_file, 'wb') as outfile:
          writer = csv.writer(outfile)
          sample_cutoff=5000
          b_counter=0
          global b
          b=[]
          for row in data:
              if counter[row[10]] >= sample_cutoff:
                 global b
                 b.append(row) 
                 writer.writerow(row)
                 #print b[b_counter]
                 b_counter+=1
      return

Answer 1

As a rule of thumb, avoid global variables.

Here, it’s easy:
let get_file return data
then you can say

data = get_file()
samples_subset1(data)

Also, I’d do all the imports on the top of the file