Python百例-41~50

本文主要是介绍Python百例-41~50，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

41-字符串格式化

"%s is %s years old" % ('bob', 23)  # 常用
"%s is %d years old" % ('bob', 23)  # 常用
"%s is %d years old" % ('bob', 23.5)  # %d是整数 常用
"%s is %f years old" % ('bob', 23.5)
"%s is %5.2f years old" % ('bob', 23.5)  # %5.2f是宽度为5，2位小数
"97 is %c" % 97
"11 is %#o" % 11  # %#o表示有前缀的8进制
"11 is %#x" % 11
"%10s%5s" % ('name', 'age')  # %10s表示总宽度为10，右对齐, 常用
"%10s%5s" % ('bob', 25)
"%10s%5s" % ('alice', 23)
"%-10s%-5s" % ('name', 'age')  # %-10s表示左对齐, 常用
"%-10s%-5s" % ('bob', 25)
"%10d" % 123
"%010d" % 123"{} is {} years old".format('bob', 25)
"{1} is {0} years old".format(25, 'bob')
"{:<10}{:<8}".format('name', 'age')

42-shutil模块常用方法

import shutilwith open('/etc/passwd', 'rb') as sfobj:with open('/tmp/mima.txt', 'wb') as dfobj:shutil.copyfileobj(sfobj, dfobj) # 拷贝文件对象shutil.copyfile('/etc/passwd', '/tmp/mima2.txt')
shutil.copy('/etc/shadow', '/tmp/')  # cp /etc/shadow /tmp/
shutil.copy2('/etc/shadow', '/tmp/')  # cp -p /etc/shadow /tmp/
shutil.move('/tmp/mima.txt', '/var/tmp/')  # mv /tmp/mima.txt /var/tmp/
shutil.copytree('/etc/security', '/tmp/anquan') # cp -r /etc/security /tmp/anquan
shutil.rmtree('/tmp/anquan')  # rm -rf /tmp/anquan
# 将mima2.txt的权限设置成与/etc/shadow一样
shutil.copymode('/etc/shadow', '/tmp/mima2.txt')
# 将mima2.txt的元数据设置成与/etc/shadow一样
# 元数据使用stat /etc/shadow查看
shutil.copystat('/etc/shadow', '/tmp/mima2.txt')
shutil.chown('/tmp/mima2.txt', user='zhangsan', group='zhangsan')

43-练习：生成文本文件

import osdef get_fname():while True:fname = input('filename: ')if not os.path.exists(fname):breakprint('%s already exists. Try again' % fname)return fnamedef get_content():content = []print('输入数据，输入end结束')while True:line = input('> ')if line == 'end':breakcontent.append(line)return contentdef wfile(fname, content):with open(fname, 'w') as fobj:fobj.writelines(content)if __name__ == '__main__':fname = get_fname()content = get_content()content = ['%s\n' % line for line in content]wfile(fname, content)

44-列表方法

alist = [1, 2, 3, 'bob', 'alice']
alist[0] = 10
alist[1:3] = [20, 30]
alist[2:2] = [22, 24, 26, 28]
alist.append(100)
alist.remove(24)  # 删除第一个24
alist.index('bob')  # 返回下标
blist = alist.copy()  # 相当于blist = alist[:]
alist.insert(1, 15)  # 向下标为1的位置插入数字15
alist.pop()  # 默认弹出最后一项
alist.pop(2) # 弹出下标为2的项目
alist.pop(alist.index('bob'))
alist.sort()
alist.reverse()
alist.count(20)  # 统计20在列表中出现的次数
alist.clear()  # 清空
alist.append('new')
alist.extend('new')
alist.extend(['hello', 'world', 'hehe'])

45-检查合法标识符

import sys
import keyword
import stringfirst_chs = string.ascii_letters + '_'
all_chs = first_chs + string.digitsdef check_id(idt):if keyword.iskeyword(idt):return "%s is keyword" % idtif idt[0] not in first_chs:return "1st invalid"for ind, ch in enumerate(idt[1:]):if ch not in all_chs:return "char in postion #%s invalid" % (ind + 2)return "%s is valid" % idtif __name__ == '__main__':print(check_id(sys.argv[1]))  # python3 checkid.py abc@123

46-创建用户，设置随机密码

randpass模块见37-生成密码/验证码

import subprocess
import sys
from randpass import gen_passdef adduser(username, password, fname):data = """user information:
%s: %s
"""subprocess.call('useradd %s' % username, shell=True)subprocess.call('echo %s | passwd --stdin %s' % (password, username),shell=True)with open(fname, 'a') as fobj:fobj.write(data % (username, password))if __name__ == '__main__':username = sys.argv[1]password = gen_pass()adduser(username, password, '/tmp/user.txt')
# python3 adduser.py john

47-列表练习：模拟栈操作

stack = []def push_it():item = input('item to push: ')stack.append(item)def pop_it():if stack:print("from stack popped %s" % stack.pop())def view_it():print(stack)def show_menu():cmds = {'0': push_it, '1': pop_it, '2': view_it}  # 将函数存入字典prompt = """(0) push it
(1) pop it
(2) view it
(3) exit
Please input your choice(0/1/2/3): """while True:# input()得到字符串，用strip()去除两端空白，再取下标为0的字符choice = input(prompt).strip()[0]if choice not in '0123':print('Invalid input. Try again.')continueif choice == '3':breakcmds[choice]()if __name__ == '__main__':show_menu()

48-实现Linux系统中unix2dos功能

import sysdef unix2dos(fname):dst_fname = fname + '.txt'with open(fname) as src_fobj:with open(dst_fname, 'w') as dst_fobj:for line in src_fobj:line = line.rstrip() + '\r\n'dst_fobj.write(line)if __name__ == '__main__':unix2dos(sys.argv[1])

49-动画程序：@从一行#中穿过

\r是回车不换行

import timelength = 19
count = 0while True:print('\r%s@%s' % ('#' * count, '#' * (length - count)), end='')try:time.sleep(0.3)except KeyboardInterrupt:print('\nBye-bye')breakif count == length:count = 0count += 1

50-字典基础用法

adict = dict()  # {}
dict(['ab', 'cd'])
bdict = dict([('name', 'bob'),('age', 25)])
{}.fromkeys(['zhangsan', 'lisi', 'wangwu'], 11)for key in bdict:print('%s: %s' % (key, bdict[key]))print("%(name)s: %(age)s" % bdict)bdict['name'] = 'tom'
bdict['email'] = 'tom@tedu.cn'del bdict['email']
bdict.pop('age')
bdict.clear()