Python Learning Notes

If you want to run the py file directly, you need to add it on the first line:

# !/usr/bin/env python

In the directory where the files are entered:

./filename.py

However, you will be prompted with an error: Permission denied, to avoid such an error, enter before the file runs:

filename.py

The invariant of the string:

When you assign a string to a variable, the contents of the variable are unchanged, unless you re-assign it to the variable.

Example: R = ' abc '

And when you run A.replace (' A ', ' a ') the function of this statement is to replace the value of a variable R with a and return the modified value with a, but the command does not re-assign the modified value to the variable R,

Therefore, you will see that the value of R stored is still ' abc '

Python Learning Notes