Master Python File Operations and System Automation with Practical Code Examples

File Operations in Python

Python provides the built‑in open() function to open files in various modes such as r, w, a, r+, w+, a+ and their binary equivalents ( rb, wb, etc.). The function returns a file object that supports methods like read(), readline(), write(), tell(), seek() and close().

Common File‑Handling Examples

Listing files in a directory and printing absolute paths:

import os
for root, dirs, files in os.walk('/tmp'):
    for name in files:
        print(os.path.join(root, name))

Printing a triangle of asterisks:

n = int(raw_input('input number:'))
for i in range(n):
    for j in range(i):
        print '*',
    print '
'

Simple number‑guessing game that creates a log file named with the current date:

import random, time, os
new_time = time.strftime('%Y-%m-%d')
f = open(new_time + '.log', 'w')
# ... write log ...

Log Analysis and Statistics

Counting IP address occurrences from a log file:

list = []
with open('/tmp/1.log') as f:
    for line in f:
        ip = line.split()[0]
        list.append(ip)
for ip in set(list):
    print '%s : %s' % (ip, list.count(ip))

Prime Number Generator

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

Web Page Retrieval

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)

Command‑Line Argument Usage

Using sys.argv to display file contents, version or help information.

Directory Traversal and File Deletion

import os

def fr(dir):
    filelist = os.listdir(dir)
    for i in filelist:
        fullfile = os.path.join(dir, i)
        if not os.path.isdir(fullfile):
            if i == "1.txt":
                os.remove(fullfile)
        else:
            fr(fullfile)

Process Memory Summation

import os
lines = os.popen('ps aux').readlines()
rss = [int(line.split()[5]) for line in lines[1:]]
print sum(rss)

Port Monitoring and Email Notification

import os, time, smtplib
while True:
    http_status = os.popen('netstat -tulnp | grep httpd').readlines()
    if not http_status:
        os.system('service httpd start')
    # send email if needed
    time.sleep(5)

Simple Authentication Loop

while True:
    user = raw_input('Please input your username:')
    if user == "wenlong":
        pwd = raw_input('Please input your pass:')
        while pwd != '123':
            pwd = raw_input('Please input your pass again:')
        print 'welcome to select system!'

CPU Monitoring via SNMP

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

Network Interface Traffic Monitoring

def getDevices(host):
    mib = getAllitems(host, 'RFC1213-MIB::ifDescr')
    return [item.split(':')[3].strip() for item in mib if re.search('eth', item)]
# ... retrieve in/out octets and print ...

The script collection demonstrates essential Python techniques for file I/O, directory traversal, log processing, system monitoring, network traffic collection and basic user interaction, providing a practical foundation for automation and operations tasks.