Exercise18、19、20、218(自定义函数， 操作文件相关函数)

ex18.py

ex19.py

Can give function straight numbers, variable, math, combine math and variable.

ex20.py

ex20_test.py

1、current_file = open(input_file)，print current_file

2、f.seek(0), 使文件指针回到文件头。"moves the file to the 0 byte (first byte) in the file"

3、f.read(), 读取全部文档，文件指针到最后。

4、f.readline(), 读取文件的一行，每次使用得到新的一行。"reading a line from the file and moving the read head to right after the \n that ends that line."

5、打印f.readline()， 行与行之间有空格。

原因： “The readline() function returns the\n thats in the file at the end of that line.”

解决办法： ”Add a end = "" at the end of“of your print function calls to avoid adding double \n to every line ”

  

ex21.py