Year: 2023

When working with strings in MicroPython on Raspberry Pi Pico, it is important to handle errors that may occur during string operations. Errors can occur for a variety of reasons, such as invalid input or incorrect syntax. Fortunately, MicroPython provides several built-in mechanisms for handling errors with strings.

One of the most common errors that can occur with strings is a ValueError due to incorrect formatting. For example, if you try to convert a string to a numeric type and the string is not a valid number, a ValueError will be raised. To handle this error, you can use a try–except block:

string = "abc123"
try:
    num = int(string)
    print(num)
except ValueError:
    print("Invalid input, cannot convert to int.")

In this example, the int() function attempts to convert the string "abc123" to an integer. However, since "abc123" is not a valid integer, a ValueError is raised. The try–except block catches the error and prints a helpful message.

Another common error that can occur with strings is an IndexError due to attempting to access an element that does not exist in a string. For example, if you try to access the 10th character of a string that only has 5 characters, an IndexError will be raised. To handle this error, you can use a similar try–except block:

string = "hello"
try:
    char = string[10]
    print(char)
except IndexError:
    print("Index out of range, cannot access character.")

In this example, we attempt to access the 10th character of the string "hello", which does not exist. An IndexError is raised, and the try–except block catches the error and prints a helpful message.

It is also possible to raise your own custom errors when working with strings. For example, you may want to raise an error if a string does not meet certain criteria. To do this, you can use the raise statement:

def process_string(string):
    if len(string) < 5:
        raise ValueError("String must be at least 5 characters long.")
    # do something with the string

In this example, the process_string() function raises a ValueError if the input string is less than 5 characters long. This allows the function to provide useful feedback to the user if the input is invalid.

In summary, handling errors with strings in MicroPython on Raspberry Pi Pico involves using try–except blocks to catch built-in errors, and raising your own custom errors when necessary. By using these mechanisms, you can ensure that your code is robust and handles unexpected situations gracefully.

Using strings with input/output operations is a common task when working with MicroPython on Raspberry Pi Pico. In this post, we will explore how to use strings with input/output operations, including reading and writing strings to files and the console.

Reading strings from the console
The easiest way to read strings from the console is to use the built-in function input(). This function reads a line of text from the console and returns it as a string.

name = input("Enter your name: ")
print("Hello,", name)

This code prompts the user to enter their name and then greets them by name.

Writing strings to the console
To output a string to the console, we can use the built-in function print(). This function takes one or more arguments, converts them to strings, and outputs them to the console.

print("Hello, world!")

This code outputs the string “Hello, world!” to the console.

Writing strings to files
To write a string to a file, we need to open the file for writing and then use the write() method to write the string to the file.

with open("output.txt", "w") as f:
    f.write("Hello, world!")

This code creates a new file called “output.txt” in the current directory and writes the string “Hello, world!” to the file.

Reading strings from files
To read a string from a file, we need to open the file for reading and then use the read() method to read the string from the file.

with open("input.txt", "r") as f:
    contents = f.read()
    print(contents)

This code reads the contents of a file called “input.txt” in the current directory and outputs the contents to the console.

String comparison is a common task in programming. In MicroPython, you can compare strings using the same comparison operators as you would in Python. This includes the “==” operator for equality, “!=” for inequality, “>” for greater than, “<” for less than, “>=” for greater than or equal to, and “<=” for less than or equal to.

It is important to note that when comparing strings, MicroPython compares the underlying Unicode code points of each character in the strings. This means that string comparison is case-sensitive, and that different characters with the same visual representation (such as accented characters or ligatures) may have different code points and therefore be considered different characters.

Here are some examples of string comparison in MicroPython:

# Equality
string1 = "Hello, world!"
string2 = "Hello, world!"
if string1 == string2:
    print("The strings are equal.")
else:
    print("The strings are not equal.")

# Inequality
string1 = "Hello, world!"
string2 = "Goodbye, world!"
if string1 != string2:
    print("The strings are not equal.")
else:
    print("The strings are equal.")

# Greater than
string1 = "apple"
string2 = "banana"
if string1 > string2:
    print("The first string is greater than the second.")
else:
    print("The first string is not greater than the second.")

# Less than
string1 = "apple"
string2 = "banana"
if string1 < string2:
    print("The first string is less than the second.")
else:
    print("The first string is not less than the second.")

In the above examples, the output would be:

The strings are equal.
The strings are not equal.
The first string is not greater than the second.
The first string is less than the second.

As mentioned earlier, string comparison in MicroPython is case-sensitive. This means that the strings “hello” and “Hello” would be considered different. If you want to perform case-insensitive string comparison, you can convert both strings to lowercase (or uppercase) before comparing them. Here is an example:

string1 = "Hello"
string2 = "hello"
if string1.lower() == string2.lower():
    print("The strings are equal, ignoring case.")
else:
    print("The strings are not equal, even ignoring case.")

In this example, the output would be “The strings are equal, ignoring case.”

Overall, string comparison in MicroPython is straightforward and follows the same principles as in Python. It is important to keep in mind the case-sensitivity of string comparison and to be aware of the differences in code points between different characters.