random ，os,sys模块

random 

import random

print(random.random()) #(0,1)----float    大于0且小于1之间的小数
print(random.randint(1, 3))  # [1,3]    大于等于1且小于等于3之间的整数

print(random.randrange(1, 3))  # [1,3)    大于等于1且小于3之间的整数

print(random.choice([111, 'aaa', [4, 5]]))  # 1或者23或者[4,5]

print(random.sample([111, 'aaa', 'ccc','ddd'],2))  # 列表元素任意2个组合

print(random.uniform(1, 3))  # 大于1小于3的小数，如1.927109612082716

item = [1, 3, 5, 7, 9]
random.shuffle(item)  # 打乱item的顺序,相当于"洗牌"
print(item)

# 应用：随机验证码
import random

def make_code(size=4):
    res=''
    for i in range(size):
        s1=chr(random.randint(65,90))
        s2=str(random.randint(0,9))
        res+=random.choice([s1,s2])
    return res

print(make_code(6))

os 

# 获取某一个文件夹下所有的子文件以及子文件夹的名字
res=os.listdir('.')
print(res)

os.remove("newname") 删除一个文件 
os.rename("oldname","newname") 重命名文件/目录

os.environ()# 规定：key与value必须都为字符串

os.environ['aaaaaaaaaa']='111'
print(os.environ)

print(os.path.dirname(r'/a/b/c/d.txt'))
print(os.path.basename(r'/a/b/c/d.txt'))
print(os.path.isfile(r'笔记.txt'))
print(os.path.isfile(r'aaa'))
print(os.path.isdir(r'aaa'))
print(os.path.join('a','/','b','c','d'))

sys

import time


def progress(percent):
    if percent > 1:
        percent = 1
    res = int(50 * percent) * '#'
    print('\r[%-50s] %d%%' % (res, int(100 * percent)), end='')


recv_size = 0
total_size = 1025011

while recv_size < total_size:
    time.sleep(0.01)

    recv_size += 1024

    # 打印进度条
    # print(recv_size)
    percent = recv_size / total_size  
    progress(percent)