Master Python File I/O and System Scripting with 10 Practical Exercises

Python provides the built‑in open('file_name', mode, buffering) function to obtain a file object; using modes such as 'r', 'w', 'a', 'r+', 'w+', 'a+', and their binary variants ( 'rb', 'wb', etc.) determines how data is accessed and whether the file is created.

Common file operations include: f.read([size]) – reads the whole file or a specific number of bytes. f.readline() – returns a single line. for line in f: – iterates over lines. f.write('text') – writes a string (convert other data to string first). f.tell() – returns the current file pointer position. f.seek(offset, whence) – moves the file pointer; whence can be 0 (start), 1 (current), or 2 (end). f.close() – closes the file.

1. List all files in a directory tree

#!/usr/bin/env python
import os
for root, dirs, files in os.walk('/tmp'):
    for name in files:
        print(os.path.join(root, name))

2. Print a right‑angled triangle

#!/usr/bin/env python
n = int(raw_input('input number:'))
for i in range(n):
    for j in range(i + 1):
        print '*',
    print '
'

3. Number‑guessing game that prints a triangle on success

#!/usr/bin/env python
import random
while True:
    guess = int(raw_input('input number:'))
    target = random.randint(1, 10)
    if guess == target:
        for i in range(guess):
            for j in range(i):
                print '*',
            print '
'
    else:
        print 'please input number again'

4. Create a daily log file and write disk usage

#!/usr/bin/env python
import time, os
date_str = time.strftime('%Y-%m-%d')
log = open(date_str + '.log', 'w')
log.write(''.join(os.popen('df -h').readlines()))
log.close()

5. Count visits per IP from a log file

#!/usr/bin/env python
ip_counts = {}
with open('/tmp/1.log') as f:
    for line in f:
        ip = line.split()[0]
        ip_counts[ip] = ip_counts.get(ip, 0) + 1
for ip, cnt in ip_counts.items():
    print '%s : %s' % (ip, cnt)

6. Validate numeric input and print all primes up to that number

#!/usr/bin/env python
while True:
    try:
        n = int(raw_input('请输入数字:').strip())
        break
    except ValueError:
        print('你输入的不是数字，请重新输入:')
for i in range(2, n + 1):
    for x in range(2, i):
        if i % x == 0:
            break
    else:
        print i

7. Demonstrate sys.argv usage

#!/usr/bin/env python
import sys
if len(sys.argv) < 2:
    print "No function be setted."
    sys.exit()
option = sys.argv[1][1:]
if option == 'version':
    print "Version1.2"
elif option == 'help':
    print "enter a filename to see the context of it!"
else:
    for filename in sys.argv[1:]:
        with open(filename) as f:
            for line in f:
                print line,

8. Simple web page fetch and first/last line extraction

from urllib import urlretrieve

def firstNonBlank(lines):
    for eachLine in lines:
        if eachLine.strip():
            return eachLine

def firstLast(webpage):
    f = open(webpage)
    lines = f.readlines()
    f.close()
    print firstNonBlank(lines)
    lines.reverse()
    print firstNonBlank(lines)

def download(url='http://www.magedu.com/72446.html', process=firstLast):
    try:
        retval = urlretrieve(url)[0]
    except IOError:
        retval = None
    if retval:
        process(retval)

if __name__ == '__main__':
    download()

9. Iterate through a directory and delete specific files

#!/usr/bin/env python
import os

def fr(dir):
    for root, dirs, files in os.walk(dir):
        for f in files:
            if f == "1.txt":
                os.remove(os.path.join(root, f))
            else:
                fr(os.path.join(root, f))

10. Sum memory usage of all processes (RSS column)

#!/usr/bin/env python
import os
lines = os.popen('ps aux').readlines()
mem_vals = []
for line in lines[1:]:
    rss = int(line.split()[5])
    mem_vals.append(rss)
print 'Total RSS:', sum(mem_vals)

11. Monitor port 80, restart httpd if closed, and send email alert

#!/usr/bin/env python
import os, time, sys, smtplib
from email.mime.text import MIMEText

def sendsimplemail(warning):
    msg = MIMEText(warning)
    msg['Subject'] = 'python first mail'
    msg['From'] = 'root@localhost'
    smtp = smtplib.SMTP()
    smtp.connect(r'smtp.126.com')
    smtp.login('user', 'pass')
    smtp.sendmail('user', ['user'], msg.as_string())
    smtp.close()

while True:
    status = os.popen('netstat -tulnp | grep httpd').readlines()
    if not status:
        os.system('service httpd start')
        sendsimplemail('httpd failed to start')
    else:
        print 'httpd running'
    time.sleep(5)

12. SNMP‑based CPU usage monitoring for multiple hosts

#!/usr/bin/env python
import os

def getAllitems(host, oid):
    return os.popen('snmpwalk -v 2c -c public %s %s' % (host, oid)).read().split('
')[:-1]

def getDate(host):
    items = getAllitems(host, '.1.3.6.1.4.1.2021.11')
    total = sum(float(item.split()[3]) for item in items)
    rates = []
    for item in items:
        rates.append(float(item.split()[3]) / total * 100)
    labels = ['%us','%ni','%sy','%id','%wa','%cpu_irq','%cpu_sIRQ']
    return list(zip(rates, labels))

if __name__ == '__main__':
    hosts = ['192.168.10.1','192.168.10.2']
    for host in hosts:
        print '==========%s==========' % host
        for val, label in getDate(host):
            print ' %.2f%s' % (val, label)

13. SNMP‑based network interface traffic monitoring

#!/usr/bin/env python
import os, re

def getAllitems(host, oid):
    return os.popen('snmpwalk -v 2c -c public %s %s' % (host, oid)).read().split('
')[:-1]

def getDevices(host):
    descr = getAllitems(host, 'RFC1213-MIB::ifDescr')
    return [item.split(':')[3].strip() for item in descr if re.search('eth', item)]

def getDate(host, oid):
    data = getAllitems(host, oid)[1:]
    return [str(round(float(item.split(':')[3].strip())/1024,2)) + ' KB' for item in data]

if __name__ == '__main__':
    hosts = ['192.168.10.1','192.168.10.2']
    for host in hosts:
        devs = getDevices(host)
        in_octets = getDate(host, 'IF-MIB::ifInOctets')
        out_octets = getDate(host, 'IF-MIB::ifOutOctets')
        print '==========%s==========' % host
        for i in range(len(devs)):
            print '%s : RX: %-15s   TX: %s' % (devs[i], in_octets[i], out_octets[i])

These examples collectively demonstrate essential Python file handling, command‑line processing, system monitoring, and network management techniques useful for beginners and intermediate developers.