Dave Hylands
9 years ago
committed by
Damien George
3 changed files with 212 additions and 6 deletions
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The MicroPython Interactive Interpreter Mode (aka REPL) |
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======================================================= |
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This section covers some characteristics of the MicroPython Interactive |
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Interpreter Mode. A commonly used term for this is REPL (read-eval-print-loop) |
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which will used to refer to this interactive prompt. |
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Auto-indent |
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----------- |
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When typing python statements which end in a colon (for example if, for, while) |
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then the prompt will change to three dots (...) and the cursor will be indented |
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by 4 spaces. When you press return, the next line will continue at the same |
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level of indentation for regular statements or an additional level of indentation |
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where appropriate. If you press the backspace key then it will undo one |
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level of indentation. |
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If your cursor is all the way back at the beginning, pressing RETURN will then |
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execute the code that you've entered. The following shows what you'd see |
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after entering a for statement (the underscore shows where the cursor winds up): |
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>>> for i in range(3): |
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... _ |
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If you then enter an if statement, an additional level of indentation will be |
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provided: |
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>>> for i in range(30): |
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... if i > 3: |
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... _ |
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Now enter ``break`` followed by RETURN and press BACKSPACE: |
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>>> for i in range(30): |
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... if i > 3: |
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... break |
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... _ |
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Finally type ``print(i)``, press RETURN, press BACKSPACE and press RETURN again: |
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>>> for i in range(30): |
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... if i > 3: |
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... break |
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... print(i) |
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... |
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0 |
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1 |
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2 |
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3 |
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>>> |
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Auto-completion |
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--------------- |
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While typing a command at the REPL, if the line typed so far corresponds to |
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the beginning of the name of something, then pressing TAB will show |
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possible things that could be entered. For example type ``m`` and press TAB |
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and it should expand to ``machine``. Enter a dot ``.`` and press TAB again. You |
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should see something like: |
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>>> machine. |
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__name__ info unique_id reset |
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bootloader freq rng idle |
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sleep deepsleep disable_irq enable_irq |
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Pin |
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The word will be expanded as much as possible until multiple possibilities exist. |
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For example, type ``machine.Pin.AF3`` and press TAB and it will expand to |
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``machine.Pin.AF3_TIM``. Pressing TAB a second time will show the possible |
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expansions: |
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>>> machine.Pin.AF3_TIM |
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AF3_TIM10 AF3_TIM11 AF3_TIM8 AF3_TIM9 |
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>>> machine.Pin.AF3_TIM |
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Interrupting a running program |
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------------------------------ |
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You can interupt a running program by pressing Ctrl-C. This will raise a KeyboardInterrupt |
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which will bring you back to the REPL, providing your program doesn't intercept the |
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KeyboardInterrupt exception. |
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For example: |
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>>> for i in range(1000000): |
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... print(i) |
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... |
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0 |
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1 |
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2 |
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3 |
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... |
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6466 |
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6467 |
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6468 |
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Traceback (most recent call last): |
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File "<stdin>", line 2, in <module> |
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KeyboardInterrupt: |
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>>> |
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Paste Mode |
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---------- |
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If you want to paste some code into your terminal window, the auto-indent feature |
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will mess things up. For example, if you had the following python code: :: |
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def foo(): |
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print('This is a test to show paste mode') |
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print('Here is a second line') |
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foo() |
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and you try to paste this into the normal REPL, then you will see something like |
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this: |
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>>> def foo(): |
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... print('This is a test to show paste mode') |
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... print('Here is a second line') |
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... foo() |
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... |
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Traceback (most recent call last): |
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File "<stdin>", line 3 |
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IndentationError: unexpected indent |
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If you press Ctrl-E, then you will enter paste mode, which essentially turns off |
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the auto-indent feature, and changes the prompt from ``>>>`` to ``===``. For example: |
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>>> |
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paste mode; Ctrl-C to cancel, Ctrl-D to finish |
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=== def foo(): |
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=== print('This is a test to show paste mode') |
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=== print('Here is a second line') |
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=== foo() |
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=== |
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This is a test to show paste mode |
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Here is a second line |
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>>> |
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Paste Mode allows blank lines to be pasted. The pasted text is compiled as if |
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it were a file. Pressing Ctrl-D exits paste mode and initiates the compilation. |
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Soft Reset |
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---------- |
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A soft reset will reset the python interpreter, but tries not to reset the |
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method by which you're connected to the MicroPython board (USB-serial, or Wifi). |
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You can perform a soft reset from the REPL by pressing Ctrl-D, or from your python |
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code by executing: :: |
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raise SystemExit |
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For example, if you reset your MicroPython board, and you execute a dir() |
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command, you'd see something like this: |
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>>> dir() |
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['__name__', 'pyb'] |
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Now create some variables and repeat the dir() command: |
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>>> i = 1 |
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>>> j = 23 |
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>>> x = 'abc' |
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>>> dir() |
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['j', 'x', '__name__', 'pyb', 'i'] |
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>>> |
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Now if you enter Ctrl-D, and repeat the dir() command, you'll see that your |
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variables no longer exist: |
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.. code-block:: python |
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PYB: sync filesystems |
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PYB: soft reboot |
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MicroPython v1.5-51-g6f70283-dirty on 2015-10-30; PYBv1.0 with STM32F405RG |
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Type "help()" for more information. |
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>>> dir() |
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['__name__', 'pyb'] |
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>>> |
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The special variable _ (underscore) |
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----------------------------------- |
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When you use the REPL, you may perfom computations and see the results. |
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MicroPython stores the results of the previous statment in the variable _ (underscore). |
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So you can use the underscore to save the result in a variable. For example: |
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>>> 1 + 2 + 3 + 4 + 5 |
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15 |
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>>> x = _ |
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>>> x |
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15 |
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>>> |
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Raw Mode |
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-------- |
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Raw mode is not something that a person would normally use. It is intended for |
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programmatic use. It essentially behaves like paste mode with echo turned off. |
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Raw mode is entered using Ctrl-A. You then send your python code, followed by |
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a Ctrl-D. The Ctrl-D will be acknowledged by 'OK' and then the python code will |
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be compiled and executed. Any output (or errors) will be sent back. Entering |
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Ctrl-B will leave raw mode and return the the regular (aka friendly) REPL. |
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The ``tools/pyboard.py`` program uses the raw REPL to execute python files on the |
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MicroPython board. |
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