博主上周起开始0基础自学python，每周都会更新一次自己的学习代码，请各位监督。
这里用的是Python3.x，用的是Mac电脑上自带的Python
一、var篇
在Unix下创建hello.py文件，输入
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
print('Hello, world!')
然后输入执行命令: python hello.py，输出
XutekiMacBook-Pro:~ xumengyuan$ python hello.python
Hello, world!
ps:执行前，需给hello.py执行权限，chmod 755 hello.py
输出一个变量：
>>> name = 'Alex Li' >>> print(name) Alex Li
当将一个变量赋给另一个变量时，观察两个变量的输出结果：
>>> name_1 = 'Alex Li' >>> name_2 = name_1 >>> name_1 = 'Xmy' >>> print(name_1) Xmy >>> print(name_2) Alex Li
可见改变初始变量name_1后，并不会影响被赋值的变量name_2的输出结果。
输出多行变量，用'''***'''：
>>> msg=''' ... print('hello world') ... name = 'Alex Li' ... print(name) ... ''' >>> print(msg) print('hello world') name = 'Alex Li' print(name)
二、interaction篇
用input()函数打到交互效果
>>> name = input('name:') name:Xmy >>> print(name) Xmy
现在，我们需要输入一个人的姓名、年龄、工作、薪水这些信息，可以用'''name'''+name的方式进行操作，具体如下：
>>> name = input('name:') name:XMY >>> age = input('age:') age:24 >>> job = input('job:') job:IT >>> salary = input('salary:') salary:2000 >>> info = ''' ... -------------info of ''' + name + '''----------- ... name:''' + name + ''' ... age:''' + str(age) + ''' ... job: ''' + job + ''' ... salary: ''' + salary >>> print(info) -------------info of XMY----------- name:XMY age:24 job: IT salary: 2000
此外，我们还可以用%s的形式来进行操作
>>> info_2 = ''' ... -------------info of %s ----------- ... name:%s ... age:%d ... job:%s ... salary:%s ... ''' % (name,name,age,job,salary) Traceback (most recent call last): File "<stdin>", line 7, in <module> TypeError: %d format: a number is required, not str
这时，我们会发现，在age:之后我们家的是%d，即规定了后面必须要用number格式来进行输入，然而在一开始age = input('age:')中，age的格式是字符串，我们可以用int()对其紧张转换成整形
>>> info_2 = ''' ... -------------info of %s ----------- ... name:%s ... age:%d ... job:%s ... salary:%s ... ''' % (name,name,age,job,salary) >>> print(info_2) -------------info of XMY ----------- name:XMY age:18 job:IT salary:2000
转换成整形后，得出结果：
>>> age = input('age:') age:18 >>> print(type(age)) <class 'str'> >>> age = int(input('age:')) age:18 >>> print(type(age)) <class 'int'>
此外，我们还可以用format进行输出，format的形式主要分为两种：
1.通过赋值：
>>> info_3 = ''' ... -------------info of {_name} ----------- ... name:{_name} ... age:{_age} ... job:{_job} ... salary:{_salary} ... '''.format(_name=name, ... _age=age, ... _job=job, ... _salary=salary) >>> print(info_3) -------------info of XMY ----------- name:XMY age:18 job:IT salary:2000
2.通过指定位置：
>>> info_4 = ''' ... -------------info of {0} ----------- ... name:{0} ... age:{1} ... job:{2} ... salary:{3} ... '''.format(name,age,job,salary) >>> print(info_4) -------------info of XMY ----------- name:XMY age:18 job:IT salary:2000
ps：这里需要指出，在python中，位置是以0开始的。
三、if...else篇
假如我们现在有一个登录界面，你已经注册号了用户名和密码，需要通过判断你输入的是否正确给出提示，我们可以通过if...else语句来实现：
>>> _username = 'Xmy' >>> _password = 'Xmy123' >>># 输入错误密码 >>> username = input('username:') username:Xmy >>> password = input('password:') password:234 >>> if _username == username and _password == password : ... print("Welcome user {name} login ...".format(name=username)) ... else: ... print("Invalid username or password.") ... Invalid username or password. # 密码或用户名错误 >>># 密码和用户名正确 >>> username = input('username:') username:Xmy >>> password = input('password:') password:Xmy123 >>> if _username == username and _password == password : ... print("Welcome user {name} login ...".format(name=username)) ... else: ... print("Invalid username or password.") ... Welcome user Xmy login ... # 欢迎登录
一般，我们登录界面的密码会显示成暗文，可以用getpass模块进行实现：
>>> import getpass >>> username = input('username:') username:Xmy >>> password = getpass.getpass('password:') #在python中显示暗文 password: >>> if _username == username and _password == password : ... print("Welcome user {name} login ...".format(name=username)) ... else: ... print("Invalid username or password.") ... Welcome user Xmy login ...
四、while循环篇
while是一种常见的循环，我们可以通过一个简单的例子来了解他的使用。
假定我们给一个初始变量赋值count赋值为0，通过while循环，让每一次循环给count加一，则可以这么实现：
count = 0 while True: print('count:',count) count += 1 # 相当于count = count+1
通过上述代码我们完成了循环目的，却发现这个循环无法结束，会一直运行下去，所以我们需要通过增加条件来终止这一段代码。
假定，我们希望在count=10时，结束代码，可以用break来实现：
>>> while True: ... print('count:',count) ... count += 1 # count = count+1 ... if count == 10: ... break ... count: 0 count: 1 count: 2 count: 3 count: 4 count: 5 count: 6 count: 7 count: 8 count: 9
现在，我们初步了解了while的使用原理后，我们可以结合之前学习的if...else来完成一个小例子。
假设我们给定一个人的年龄，来猜测他的真实年龄，并给错误结果给出相应的提示，而猜的机会只有三次，超过三次猜错，则退出程序。
可以通过如下代码实现：
>>> age_of_oldboy = 56
>>> count = 0 >>> while count <3: ... guess_age = int(input('guess age:')) ... if guess_age == age_of_oldboy: ... print('yes, you got it!') ... break ... elif guess_age > age_of_oldboy: ... print('think smaller...') ... else: ... print('think bigger...') ... count += 1 ... else: ... print('you have tried too many times... Fuck off!') ... guess age:1 think bigger... guess age:7 think bigger... guess age:89 think smaller... you have tried too many times... Fuck off!
现在，我们队这个小程序做一些改进。
如果三次猜错后，会出现“是否要继续？”的提示，如果要继续，则回答y，重新进入循环，如果希望退出，则回答n，退出循环：
>>> age_of_oldboy = 56 >>> count = 0 >>> while count <3: ... guess_age = int(input('guess age:')) ... if guess_age == age_of_oldboy: ... print('yes, you got it!') ... break ... elif guess_age > age_of_oldboy: ... print('think smaller...') ... else: ... print('think bigger...') ... count += 1 ... if count == 3: ... continue_confirm = input('Do you want ot keep trying?(y/n)') ... if continue_confirm != 'n': ... count = 0 ... else: ... print('you have tried too many times... Fuck off!') ... guess age:46 think bigger... guess age:58 think smaller... guess age:50 think bigger... Do you want ot keep trying?(y/n)y guess age:36 think bigger... guess age:50 think bigger... guess age:54 think bigger... Do you want ot keep trying?(y/n)n you have tried too many times... Fuck off!
五、for循环篇
for循环作为另一种十分常见的循环，相比while循环更为简洁：
>>> for i in range(10): ... print('loop:',i) ... loop: 0 loop: 1 loop: 2 loop: 3 loop: 4 loop: 5 loop: 6 loop: 7 loop: 8 loop: 9
在这里，需要对range()做一个特别的介绍，如果我们要取0-9中偶数可以写成range(0,10,2)
最后，我们用for循环来完成之前的拿到例题：
>>> age_of_oldboy = 56 >>> >>> >>> count = 0 >>> for i in range(3): ... guess_age = int(input('guess age:')) ... if guess_age == age_of_oldboy: ... print('yes, you got it!') ... break ... elif guess_age > age_of_oldboy: ... print('think smaller...') ... else: ... print('think bigger...') ... else: ... print('you have tried too many times... Fuck off!') ... guess age:2 think bigger... guess age:57 think smaller... guess age:54 think bigger... you have tried too many times... Fuck off!
