Blocks#

This is Exercise 2 of the Micro Python Tutorial.

In Python, a block is a group of statements that belong together, forming the body of a function, loop, class or other structure. A block is defined by an initial line followed by the contents of the block indented four characters.

As an example, a for block sets up a loop:

main.py
for i in range(0,5): print(i)
Notice that the contents of the for block are indented four characters. This causes the contents of the block to be executed five times, printing the value of the index variable ("i") each time.

The try-except-finally Block#

There is a try-except-finally structure called a compound statement, consisting of three separate blocks. This is ideal for a main.py file, and is also a very common and useful structure. It is composed of three parts:

  • try: this block contains is the code we want to try to execute
  • except: this block catches any errors or exceptions that occur and executes the block, handling the exception
  • finally: no matter what happens, this block will be executed after the try (and possibly except) blocks are executed

In the below example, there is a try block, followed by an except block, followed by a finally block. A try block must be followed by an except block and/or a finally block (you must have one of them).

main.py
try:

print('hello world.') # remember to indent the insides of your blocks by 4 characters!

except Exception: # this block is executed if there is an exception (error) print('an error occurred.') finally: # this is always executed, no matter what print('complete.')

If you want to use the exception to print out an error message you need to assign it to a variable (in this case, we've used ex).

main.py
try:

print('hello world.')

except Exception as ex: # we assign the Exception to the variable 'ex' print('an error occurred: {}'.format(ex)) finally: print('complete.')

Optional Blocks#

As mentioned above, in the try-except-finally compound statement, the except or finally block is optional.

If you don't need to do anything after exiting the try block you can leave off the finally block:

main.py
try:

print('hello world.')

except Exception: print('an error occurred.')

or, just using finally:

main.py
try:

print('hello world.')

finally: print('complete.')

This would be useful when you want the Exception to be passed on and handled somewhere else.

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Next: MicroPython Tutorial Exercise 3: functions

This page (revision-16) was last changed on 2025-07-30 12:48 by Murray AltheimTop