python基础第一课,,一 python第一
python基础第一课,,一 python第一
一 python第一个程序
print(‘hello world!‘) # python3.x print ‘hello world!‘ # python2.x
二 变量
2.1 变量名称规则
变量名只能是 字母、数字或下划线的任意组合变量名的第一个字符不能是数字以下关键字不能声明为变量名[‘and‘, ‘as‘, ‘assert‘, ‘break‘, ‘class‘, ‘continue‘, ‘def‘, ‘del‘, ‘elif‘, ‘else‘, ‘except‘, ‘exec‘, ‘finally‘, ‘for‘, ‘from‘, ‘global‘, ‘if‘, ‘import‘, ‘in‘, ‘is‘, ‘lambda‘, ‘not‘, ‘or‘, ‘pass‘, ‘print‘, ‘raise‘, ‘return‘, ‘try‘, ‘while‘, ‘with‘, ‘yield‘]
2.2 案例
_name = ‘sam‘ # 正确1name = ‘yang‘ # 错误name_it_1 = ‘yuyu‘ # 正确
2.3 代码案例
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gao# print("Hello world")name = "Sam Gao" # name -----> "Sam Gao" name2 = name # name -----> "Sam Gao" and name2 -----> "Sam Gao" print(‘My name is‘, name, name2) # 输出: My name is Sam Gao Sam Gaoname = ‘pao che ge‘ # name -----> "pao che ge" and name2 -----> "Sam Gao" print(name, name2) # 输出: pao che ge Sam Gao
三 字符编码
3.1 ascii
ASCII(American Standard Code for Information Interchange,美国标准信息交换代码)是基于拉丁字母的一套电脑编码系统,主要用于显示现代英语和其他西欧语言,其最多只能用 8 位来表示(一个字节),即:2**8 = 256-1,所以,ASCII码最多只能表示 255 个符号。注:python2.x 默认使用ascii编码
3.2 中文字符集
GB2312
一共收录了7445个字符,包括6763个汉字和682个其它符号。汉字区的内码范围高字节从B0-F7,低字节从A1-FE,占用的码位是72*94=6768。其中有5个空位是D7FA-D7FE。
GBK
GB2312 支持的汉字太少。1995年的汉字扩展规范GBK1.0收录了21886个符号,它分为汉字区和图形符号区。汉字区包括21003个字符。
GB18030
2000年的 GB18030是取代GBK1.0的正式国家标准。该标准收录了27484个汉字,同时还收录了藏文、蒙文、维吾尔文等主要的少数民族文字。现在的PC平台必须支持GB18030,对嵌入式产品暂不作要求。所以手机、MP3一般只支持GB2312。
从ASCII、GB2312、GBK 到GB18030,这些编码方法是向下兼容的,即同一个字符在这些方案中总是有相同的编码,后面的标准支持更多的字符。在这些编码中,英文和中文可以统一地处理。区分中文编码的方法是高字节的最高位不为0。
按照程序员的称呼,GB2312、GBK到GB18030都属于双字节字符集 (DBCS)。繁体中文,big5。
GB2312 GBK GB18030 占两个字节,并且能够向下兼容 GB18030 --> GBK --> GB2312 --> ASCILL
3.3 unicode
Unicode(统一码、万国码、单一码)是一种在计算机上使用的字符编码。Unicode 是为了解决传统的字符编码方案的局限而产生的,它为每种语言中的每个字符设定了统一并且唯一的二进制编码,规定虽有的字符和符号最少由 16 位来表示(2个字节)
注:python3.x 默认使用unicode编码
3.4 utf-8
UTF-8,是对Unicode编码的压缩和优化,他不再使用最少使用2个字节,而是将所有的字符和符号进行分类:ascii码中的内容用1个字节保存、欧洲的字符用2个字节保存,东亚的字符用3个字节保存...
3.5 案例
#!/usr/bin/env python# encoding: utf-8 # 告诉解释器用utf-8编码# Author: Sam Gaoname = ‘高绍阳‘ # python2.x print name
#!/usr/bin/env python3# Author: Sam Gaoname = ‘高绍阳‘ # 默认用unicode编码print(name)
四 input 输入
4.1 简单输入
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gaoimport getpass_username = ‘sam‘_password = ‘123456‘username = input(‘username:‘)passwd = getpass.getpass(‘password:‘) # 在pycharm里面用不了,只能在交互式或者 在linux里以 python3 passwd.py 执行,作用:不会显示输入内容if _username == username and _password == passwd: print(‘welcome user {name} login‘.format(name=username))else: print(‘Invaild username or password‘)
4.2 案例 猜年龄游戏
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gaoage_of_sam = 28while True: guess_age = int(input(‘guess age:‘)) if age_of_sam == guess_age: print(‘yes, you got it‘) elif age_of_sam > guess_age: print(‘think big‘) else: print(‘think small‘)
五 while for循环 和 if判断
5.1 while True:
# 参考 4.2 案例 猜年龄游戏 当不知道循环到哪里的时候,就使用
5.2 案例
知识点:1. 有while......else.....的形式; 2. break和continus的用法;if 和 if.....elif...else 和 if...else
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gaoage_of_sam = 28count = 0‘‘‘猜三次,如果猜正确,则退出‘‘‘# while True:# if count == 3:# break## guess_age = int(input(‘guess age:‘))## if age_of_sam == guess_age:# print(‘yes, you got it‘)# break## elif age_of_sam > guess_age:# print(‘think big‘)# else:# print(‘think small‘)## count += 1###################################################### while count < 3:# guess_age = int(input(‘guess age:‘))## if age_of_sam == guess_age:# print(‘yes, you got it‘)# break## elif age_of_sam > guess_age:# print(‘think big‘)# else:# print(‘think small‘)## count += 1# if count == 3:# print(‘you guess too many times, fuck you !‘)####################################################### 或者while count < 3: guess_age = int(input(‘guess age:‘)) if age_of_sam == guess_age: print(‘yes, you got it‘) break elif age_of_sam > guess_age: print(‘think big‘) else: print(‘think small‘) count += 1else: print(‘you guess too many times, fuck you !‘)
5.3 使用for只玩3次
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gaoage_of_sam = 28for i in range(3): guess_age = int(input(‘guess age:‘)) if age_of_sam == guess_age: print(‘yes, you got it‘) break elif age_of_sam > guess_age: print(‘think big‘) else: print(‘think small‘)else: print(‘you guess too many times, fuck you !‘)for i in range(1, 12, 3): # 3代表步长 print(‘loop:‘, i)
5.4 任性玩5.2的游戏
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gaoage_of_sam = 28count = 0while count < 3: # while True: guess_age = int(input(‘guess age:‘)) if age_of_sam == guess_age: print(‘yes, you got it‘) break # break 结束整个循环,不结束父循环 elif age_of_sam > guess_age: print(‘think big‘) else: print(‘think small‘) count += 1 if count == 3: while True: continue_play = input(‘Do you want to play:[yes/no]:‘) if continue_play == ‘yes‘: count = 0 break elif continue_play == ‘no‘: break else: print(‘pls input valid string‘) continue # continus 跳出当前循环else: print(‘you guess too many times, fuck you !‘)
六 字符串格式化
案例
#!/usr/bin/env python3# encoding: utf-8# Author: Sam Gao# username = input(‘usrname:‘)# password = input(‘password:‘)## print(‘username:‘, username)# print(‘password:‘, password)name = input(‘name:‘) # ===== python2 raw_input python3 eval(input) ===== python2 inputage = int(input(‘age:‘)) # 默认输出的是字符串job = input(‘job:‘)salary = int(input(‘salary:‘))print(‘name:‘, type(name), ‘age‘, type(age))info = ‘‘‘----------------info of %s---------------Name: %sAge: %dJob: %sSalary: %d‘‘‘ % (name, name, age, job, salary)# %s 字符串 %d 整数 %f 浮点数info2 = ‘‘‘----------------info of {_name}---------------Name: {_name}Age: {_age}Job: {_job}Salary: {_salary}‘‘‘.format(_name=name, _age=age, _job=job, _salary=salary)info3 = ‘‘‘----------------info of {0}---------------Name: {0}Age: {1}Job: {2}Salary: {3}‘‘‘.format(name, age, job, salary)print(info)print(info2)print(info3)
python基础第一课
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