How to read and write csv on RaspberryPi Pico series ~ MicroPython ~

Introduction

In this blog post, I will explain how to use CSV files in MicroPython for the Raspberry Pi Pico series.

When using the Pico series, you may sometimes think, “I want to output this data in CSV format.

MicroPython’s firmware allows you to use the virtual file system and Python’s powerful string processing, so you can read and write CSVs just like you would on a PC, including skip headers and comma delimiters.

It is just the right file format for a little input/output. Please take a look if you are interested.

Environment

The environment used in this blog post is the following.

Connection with RaspberryPi Pico series

The Pico series can be used by itself. The Pico series can be used by itself.

Parts in use

Ready-to-use kits are also available.

Ready to use kits with soldered headers, USB cable and pin layout chart are also available.

Freenove Raspberry Pi Pico 2 (Arduino IDEに対応) 予めサルモールされたヘッダー、デュアルアームCortex-M33とデュアルHazard3 RISC-Vマイクロコントローラ、開発ボード、チュートリアルおよび例のプロジェクト

Freenove

¥2,080 （2024/11/27 21:42時点 | Amazon調べ）

口コミを見る

Amazon

ポチップ

Program overview

The program outline for this blog post is as follows.

Results of running the program

The following is the result of running the program described below.

After the CSV file is created, its contents are displayed in the terminal part of Thonny.

If the file does not appear after running the program, try clicking “Refresh” from the settings.

Entire code

The full text of the Code is as follows. The details are explained in the section “Key Points of the Code” below.

import os

# Specify a filename
fileName = "pico_spec.csv"

# Open the file in write mode
f = open( fileName,  'w')

# Write content
f.write("Name,Price,Wireless\n")
f.write("Pico,$4,No\n")
f.write("Pico W,$7,Yes\n")
f.write("Pico 2,$5,No\n")

# Closes the file when writing is complete. 
f.close()

# Reopen the file in read mode 
f = open(fileName, "r")

# Skip headers.
next(f)

# Reads lines one by one and displays them separated by commas
for line in f:
    words = line.split(",")
    print( "Name: " + words[0] )
    print( "Price: " + words )
    print( "Wireless: " + words )

# Closes the file when writing is complete.
f.close()

Key Points of the Code

Writing CSV files

In the openfunction, specify “w” for write and a file name to open the file in write mode (or create a new file if no file exists).

After opening, use the writefunction to enter headers (information such as item names) on the first line, separated by commas.
On the next line, enter the contents of the items, separated by commas.

When you have finished writing, close the file using the closefunction.

# Open the file in write mode
f = open( fileName,  'w')

# Write content
f.write("Name,Price,Wireless\n")
f.write("Pico,$4,No\n")
f.write("Pico W,$7,Yes\n")
f.write("Pico 2,$5,No\n")

# Closes the file when writing is complete. 
f.close()

Reading CSV Files

As with writing, specify “r” to read and a filename in the open function to open the file.

# Reopen the file in read mode 
f = open(fileName, "r")

Skipping headers

After the file is opened, it is read line by line, but the first line is the header (item name), which can get in the way if you want to use the data part of the file.

Therefore, the nextfunction is used to skip reading the first line.

# Skip headers.
next(f)

Split by comma

After skipping the header, the data rows are read one by one in a for loop.
Specify a comma in thesplitfunction to split each element into a list.

Once the above is done, each element of the CSV can be accessed by index. (In this case, print to view each element)

# Reads lines one by one and displays them separated by commas
for line in f:
    words = line.split(",")
    print( "Name: " + words[0] )
    print( "Price: " + words )
    print( "Wireless: " + words )

# Closes the file when writing is complete.
f.close()

Finally

In this blog post, I explained how to use CSV files with MicroPython in the Raspberry Pi Pico series.

JSON and XML are also convenient, but CSV files are more convenient for quick input/output.

With Pico series + MicroPython, you can read and write CSV files just as easily as when using Python on a PC.

Knowing this makes it easier to improve and debug, so if you are interested, please give it a try.

I would be happy to be of help.

質問・要望 大歓迎です

「こんな解説記事作って」「こんなことがしたいけど、〇〇で困ってる」など、コメント欄で教えてください。 質問・要望に、中の人ができる限り対応します。

使えたよ・設定できたよの一言コメントも大歓迎。気軽に足跡を残してみてください。記事を紹介したい方はブログ、SNSにバシバシ貼ってもらってOKです。