File34. Дан файл целых чисел. Удалить из него все отрицательные числа.

Решение на Python 3:

# -*- coding: utf-8 -*-
import random
import sys
import os

def GenerateNumbers(fname):
    N = random.randint(1,20)
    print("N = ",N)
    try:
        f = open(fname, "w")
        for i in range(0,N):
            x = random.randrange(-9,10)
            #x = i + 1
            line = str(x)+"\n"
            f.write(line)
        f.close()
    except:
        print("Error: ", sys.exc_info()[0])

f_input = "file34_in.txt"
f_output = "file34_out.txt"
GenerateNumbers(f_input)
print("Read from:",f_input)
print("Write to:",f_output)

try:
    with open(f_input, 'r') as f_in, open(f_output, 'w') as f_out:
        for line in f_in:
            x = int(line)
            if x >= 0:
                f_out.write(line)

except:
    print("Error: ", sys.exc_info())