1-while-break
break is to end the loop. After the break, the code in the loop body will not be executed.
while True:
yn = input('Continue(y/n): ')
if yn in ['n', 'N']:
break
print('running...')
2-while-continue
Calculates the sum of even numbers up to 100.
continue is to skip the rest of the loop and return to the loop condition.
sum100 = 0
counter = 0
while counter < 100:
counter += 1
# if counter % 2:
if counter % 2 == 1:
continue
sum100 += counter
print(sum100)
3-for loop through the data object
astr = 'hello'
alist = [10, 20, 30]
atuple = ('bob', 'tom', 'alice')
adict = {'name': 'john', 'age': 23}
for ch in astr:
print(ch)
for i in alist:
print(i)
for name in atuple:
print(name)
for key in adict:
print('%s: %s' % (key, adict[key]))
4-range usage and digital accumulation
# range(10) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
# >>> list(range(10))
# range(6, 11) # [6, 7, 8, 9, 10]
# range(1, 10, 2) # [1, 3, 5, 7, 9]
# range(10, 0, -1) # [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
sum100 = 0
for i in range(1, 101):
sum100 += i
print(sum100)
5- list implements Fibonacci sequence
Given two numbers first in the list, the next number is always the sum of the first two numbers.
fib = [0, 1]
for i in range(8):
fib.append(fib[-1] + fib[-2])
print(fib)
6-nine-nine multiplication table
for i in range(1, 10):
for j in range(1, i + 1):
print('%s*%s=%s' % (j, i, i * j), end=' ')
print()
# i=1 ->j: [1]
# i=2 ->j: [1,2]
# i=3 ->j: [1,2,3]
# 由用户指定相乘到多少
n = int(input('number: '))
for i in range(1, n + 1):
for j in range(1, i + 1):
print('%s*%s=%s' % (j, i, i * j), end=' ')
print()
7- Step by step implementation of list comprehension
# 10+5 的结果放到列表中
[10 + 5]
# 10+5 这个表达式计算 10 次
[10 + 5 for i in range(10)]
# 10+i 的 i 来自于循环
[10 + i for i in range(10)]
[10 + i for i in range(1, 11)]
# 通过 if 过滤，满足 if 条件的才参与 10+i 的运算
[10 + i for i in range(1, 11) if i % 2 == 1]
[10 + i for i in range(1, 11) if i % 2]
# 生成 IP 地址列表
['192.168.1.%s' % i for i in range(1, 255)]
8-Rock-paper-scissors best-of-three
import random
all_choices = ['石头', '剪刀', '布']
win_list = [['石头', '剪刀'], ['剪刀', '布'], ['布', '石头']]
prompt = """(0) 石头
(1) 剪刀
(2) 布
请选择 (0/1/2): """
cwin = 0
pwin = 0
while cwin < 2 and pwin < 2:
computer = random.choice(all_choices)
ind = int(input(prompt))
player = all_choices[ind]
print("Your choice: %s, Computer's choice: %s" % (player, computer))
if player == computer:
print('\033[32;1m 平局、033[0m')
elif [player, computer] in win_list:
pwin += 1
print('\033[31;1mYou WIN!!!\033[0m')
else:
cwin += 1
print('\033[31;1mYou LOSE!!!\033[0m')
9- Basic operation of file object
# 文件操作的三个步骤：打开、读写、关闭
# cp /etc/passwd /tmp
f = open('/tmp/passwd') # 默认以 r 的方式打开纯文本文件
data = f.read() # read() 把所有内容读取出来
print(data)
data = f.read() # 随着读写的进行，文件指针向后移动。
# 因为第一个 f.read() 已经把文件指针移动到结尾了，所以再读就没有数据了
# 所以 data 是空字符串
f.close()
f = open('/tmp/passwd')
data = f.read(4) # 读 4 字节
f.readline() # 读到换行符、n 结束
f.readlines() # 把每一行数据读出来放到列表中
f.close()
################################
f = open('/tmp/passwd')
for line in f:
print(line, end='')
f.close()
##############################
f = open('图片地址', 'rb') # 打开非文本文件要加参数 b
f.read(4096)
f.close()
##################################
f = open('/tmp/myfile', 'w') # 'w'打开文件，如果文件不存在则创建
f.write('hello world!\n')
f.flush() # 立即将缓存中的数据同步到磁盘
f.writelines(['2nd line.\n', 'new line.\n'])
f.close() # 关闭文件的时候，数据保存到磁盘
##############################
with open('/tmp/passwd') as f:
print(f.readline())
#########################
f = open('/tmp/passwd')
f.tell() # 查看文件指针的位置
f.readline()
f.tell()
f.seek(0, 0) # 第一个数字是偏移量，第 2 位是数字是相对位置。
# 相对位置 0 表示开头，1 表示当前，2 表示结尾
f.tell()
f.close()
10-Copy files
To copy a file is to open the source file with r, open the target file with w, read the source file data, and write it to the target file.
Here's the [NOT RECOMMENDED] way, but it will work:
f1 = open('/bin/ls', 'rb')
f2 = open('/root/ls', 'wb')
data = f1.read()
f2.write(data)
f1.close()
f2.close()
11-Copy files
Read 4K each time, until the end of reading:
src_fname = '/bin/ls'
dst_fname = '/root/ls'
src_fobj = open(src_fname, 'rb')
dst_fobj = open(dst_fname, 'wb')
while True:
data = src_fobj.read(4096) # 每次读取 4K
if not data:
break
dst_fobj.write(data)
src_fobj.close()
dst_fobj.close()
12 - Positional parameters
Note: Numbers in positional parameters are in character form
import sys
print(sys.argv) # sys.argv 是 sys 模块里的 argv 列表
# python3 position_args.py
# python3 position_args.py 10
# python3 position_args.py 10 bob
13-Function Application-Fibonacci Sequence
def gen_fib(l):
fib = [0, 1]
for i in range(l - len(fib)):
fib.append(fib[-1] + fib[-2])
return fib # 返回列表，不返回变量 fib
a = gen_fib(10)
print(a)
print('-' * 50)
n = int(input("length: "))
print(gen_fib(n)) # 不会把变量 n 传入，是把 n 代表的值赋值给形参
14-function-copy file
import sys
def copy(src_fname, dst_fname):
src_fobj = open(src_fname, 'rb')
dst_fobj = open(dst_fname, 'wb')
while True:
data = src_fobj.read(4096)
if not data:
break
dst_fobj.write(data)
src_fobj.close()
dst_fobj.close()
copy(sys.argv[1], sys.argv[2])
# 执行方式
# cp_func.py /etc/hosts /tmp/zhuji.txt
15-Function-99 Multiplication Table
def mtable(n):
for i in range(1, n + 1):
for j in range(1, i + 1):
print('%s*%s=%s' % (j, i, i * j), end=' ')
print()
mtable(6)
mtable(9)
16 - Module Basics
Every file with a py extension is a module.
star.py：
hi = 'hello world!'
def pstar(n=50):
print('*' * n)
if __name__ == '__main__':
pstar()
pstar(30)
Call the star module in call_star.py:
import star
print(star.hi)
star.pstar()
star.pstar(30)
17-Generate Password/Verification Code
This file is named: randpass.py
Ideas:
1. Set a basic string for randomly extracting characters. In this example, use uppercase and lowercase letters plus numbers
2. Loop n times, randomly take out a character each time
3. Stitch each character together and save it in the variable result
from random import choice
import string
all_chs = string.ascii_letters + string.digits # 大小写字母加数字
def gen_pass(n=8):
result = ''
for i in range(n):
ch = choice(all_chs)
result += ch
return result
if __name__ == '__main__':
print(gen_pass())
print(gen_pass(4))
print(gen_pass(10))
18 - Sequence Object Methods
from random import randint
alist = list() # []
list('hello') # ['h', 'e', 'l', 'l', 'o']
list((10, 20, 30)) # [10, 20, 30] 元组转列表
astr = str() # ''
str(10) # '10'
str(['h', 'e', 'l', 'l', 'o']) # 将列表转成字符串
atuple = tuple() # ()
tuple('hello') # ('h', 'e', 'l', 'l', 'o')
num_list = [randint(1, 100) for i in range(10)]
max(num_list)
min(num_list)
19 - Sequence object method 2
alist = [10, 'john']
# list(enumerate(alist)) # [(0, 10), (1, 'john')]
# a, b = 0, 10 # a->0 ->10
for ind in range(len(alist)):
print('%s: %s' % (ind, alist[ind]))
for item in enumerate(alist):
print('%s: %s' % (item[0], item[1]))
for ind, val in enumerate(alist):
print('%s: %s' % (ind, val))
atuple = (96, 97, 40, 75, 58, 34, 69, 29, 66, 90)
sorted(atuple)
sorted('hello')
for i in reversed(atuple):
print(i, end=',')
20 - String Methods
py_str = 'hello world!'
py_str.capitalize()
py_str.title()
py_str.center(50)
py_str.center(50, '#')
py_str.ljust(50, '*')
py_str.rjust(50, '*')
py_str.count('l') # 统计 l 出现的次数
py_str.count('lo')
py_str.endswith('!') # 以！结尾吗？
py_str.endswith('d!')
py_str.startswith('a') # 以 a 开头吗？
py_str.islower() # 字母都是小写的？其他字符不考虑
py_str.isupper() # 字母都是大写的？其他字符不考虑
'Hao123'.isdigit() # 所有字符都是数字吗？
'Hao123'.isalnum() # 所有字符都是字母数字？
' hello\t '.strip() # 去除两端空白字符，常用
' hello\t '.lstrip()
' hello\t '.rstrip()
'how are you?'.split()
'hello.tar.gz'.split('.')
'.'.join(['hello', 'tar', 'gz'])
'-'.join(['hello', 'tar', 'gz'])