3. The internal filesystem

If your devices has 1Mbyte or more of storage then it will be set up (upon first boot) to contain a filesystem. This filesystem uses the FAT format and is stored in the flash after the MicroPython firmware.

3.1. Creating and reading files

MicroPython on the ESP8266 supports the standard way of accessing files in Python, using the built-in open() function.

To create a file try:

>>> f = open('data.txt', 'w')
>>> f.write('some data')
>>> f.close()

The “9” is the number of bytes that were written with the write() method. Then you can read back the contents of this new file using:

>>> f = open('data.txt')
>>> f.read()
'some data'
>>> f.close()

Note that the default mode when opening a file is to open it in read-only mode, and as a text file. Specify 'wb' as the second argument to open() to open for writing in binary mode, and 'rb' to open for reading in binary mode.

3.2. Listing file and more

The os module can be used for further control over the filesystem. First import the module:

>>> import os

Then try listing the contents of the filesystem:

>>> os.listdir()
['boot.py', 'port_config.py', 'data.txt']

You can make directories:

>>> os.mkdir('dir')

And remove entries:

>>> os.remove('data.txt')

3.3. Start up scripts

There are two files that are treated specially by the ESP8266 when it starts up: boot.py and main.py. The boot.py script is executed first (if it exists) and then once it completes the main.py script is executed. You can create these files yourself and populate them with the code that you want to run when the device starts up.

3.4. Accessing the filesystem via WebREPL

You can access the filesystem over WebREPL using the provided command-line tool. This tool is found at https://github.com/micropython/webrepl and is called webrepl_cli.py. Please refer to that program for information on how to use it.