It is new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

It is new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications:

• December 2018

It is new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

Structures comparing

Sometimes you want to compare complex structures in tests ignoring some values. Usually, it can be done by comparing particular values with the structure:

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

0_0

0_0 is a totally valid Python expression.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

← Previous publications

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

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The \ symbol in regular string have special meaning. \t is tab character, \r is carriage return and so on.

You can use raw-strings to disable this behaviour. r'\t' is just backslash and t.

You obviously can’t use ' inside r'...'. However, it still can be escaped by \, but \ is preserved in the string:

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You can’t mutate closure variables by simply assigning them. Python treats assignment as a definition inside a function body and doesn’t make closure at all.

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If an instance of a class doesn’t have an attribute with the given name, it tries to access the class attribute with the same name.

>>> class A:
...     x = 2
...
>>> A.x
2
>>> A().x
2

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It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

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If you want to iterate over several iterables at once, you can use the zip function (it has nothing to do with ZIP file format):

Tips and tricks from my Telegram-channel @pythonetc, November 2019

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

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PATH is an environment variable that stores paths where executables are looked for. When you ask your shell to run ls, the shell looks for the ls executable file across all paths that are presented in PATH.

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Different asyncio tasks obviously have different stacks. You can view at all of them at any moment using asyncio.all_tasks() to get all currently running tasks and task.get_stack() to get a stack for each task.

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The order of except blocks matter: if exceptions can be caught by more than one block, the higher block applies. The following code doesn’t work as intended: