Gain insights into Python by exploring basic to advanced concepts, including loops, classes, and GUIs with Tkinter. Delve into testing and become a productive Python programmer.

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In this course, you will get a comprehensive overview of Python. You will start by laying the foundation and learning the introductory topics like operators, conditional statements, functions, loops, assignment statements, and more. You will then move onto more advanced topics such as classes and inheritance, iterators, list comprehensions, and dictionaries. Along with this, you will also get to explore the concept of testing and take a look at how GUI applications can be designed using Tkinter, Python's standard GUI library. 

By the time you're done, you'll be able to hit the ground running and be equipped with the tools that will allow you to be productive in Python.

Python 3: From Beginner to Advanced

# Introduction to file handling

To read or write a file, you must do three things: 
1. Open the file 
2. Use the file (reading or writing)
3. Close the file

# Opening files in Python

The `file = open(file_name, mode)` command opens and returns (in the variable `file`) a reference to the named file. In this case, `mode` would be one of the following:
  - `r` to **read** the file (This is the **default** if `mode` is omitted).
  - `w` to **erase and write** the file.
  - `a` to **append to the end** of an **existing** file.
  - `r+` to both **read and write**.
  - `rb`, `wb`, `ab`, and `rb+` to do **binary** input/output.

An example of this can be:
```python
file = open(file_name) # mode omitted (r used by default) so file is being read     
file = open(file_name,'w') # w used here so writing to file
```

# File methods in Python

The following are some of the methods that come along with the file object in Python:

- `file.read()` will **read in** and return the **entire** file as a **single string**, including any newline characters.
- `file.readline()` **reads** and returns a **line of text**, including the terminating newline (if any). If the **empty string** is returned, the **end of the file** has been reached.
- `file.readlines()` **reads the entire** file and returns it as a **list of strings**, including terminating newlines.
- `file.write(string)` **writes the string** to the file, and it returns the **number of characters** written.

An alternative of using the `read`, `readline` and `readlines` methods can be iterating over them using a loop. For example: 
```python
for line in file:
  statements
``` 
The above code will **read each line** in the file, **assign** it to the variable line, and **execute** the `statements`. Here, the `statements` are indented as usual.

# Closing files in Python

Closing the file is a **mandatory** step as leaving the file open when you are done with it is likely to cause problems. The `file.close()` command is used for **closing** the file.

An example of this can be:
```python
file = open(file_name) # file being read
file.close() # closing the file
```
An excellent alternative to closing files in Python is using the `with` operator. 
```python
with open(file_name) as file: 
  statements
```
The above code will **open** the file, **execute** the `statements` **once**, and automatically **close** the file without explicitly using the `close` method. 

> **Note**: Since the `statements` are executed only once, they typically consist of a loop to read and process each line in turn. Indentation is as usual, meaning the `statements` are indented under the `with` line.

# Files example

The following is an example of reading a text file, printing its contents, and closing the file:

In this lesson, you'll learn how to read and write files in Python. 

Introduction

The Absolute Bare Minimum

Better Tools

Classes

Getting Fancy

Testing

Graphical User Interfaces

Modules

Appendix

I Guess We're Doing Python Now Exam

File I/O

Introduction to file handling

Opening files in Python