open()中的有俩个形参，一个提供需要打开的文件的名称，一个提供文件的打开方式
打开方式有：r、r+、rb、w、w+、wb、a、a+、ab等
r：只读模式
w：写入模式
a：附加模式
b：二进制格式
+：可读可写
准备一个文件：
test.txt
In Python you can:do1
In Python you can:do2
In Python you can:do3
比踩踩，还干显示
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代码尝试：
r
with open('..\AutoTest\test.txt', 'r') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件不变
rb
with open('..\AutoTest\test.txt', 'rb') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件不变
r+
with open('..\AutoTest\test.txt', 'r+') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件更新
w
with open('..\AutoTest\test.txt', 'w') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件未空
wb
with open('..\AutoTest\test.txt', 'wb') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件为空
w+
with open('..\AutoTest\test.txt', 'w+') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件更新
a
with open('..\AutoTest\test.txt', 'a') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件不变
ab
with open('..\AutoTest\test.txt', 'ab') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件不变
a+
with open('..\AutoTest\test.txt', 'a+') as filename: context = filename.read() print(context) filename.write('测试插入') filename.close() |
文件更新
总结
如果打开模式是w或a，没有+的话，是无法读取文件的
w相当于重写文件，a是对文件末尾进行添加，w+和a+针对不存在的文件是会新建的
而打开模式是r，没有+，是无法编辑文件的，r+不会创建不存在的文件
为什么后面几个案例执行read()，打印出来的内容为空？