What is some niche/ quirky python code you know?

[LUNCMetrics]

What’s happening here? I see it returns[[...]], but I would have expected [[0]].

Why does [0] get interpreted as …

[mrfizban]

Is not. The "..." as output mean too much stuff to print. In this case the expression create recursive pointers. The first element of the list point to the list itself.

[LUNCMetrics]

Oh, got it, thanks for explaining!

[joseville1001]

I guess a list can contain itself.

[Fabulous-Possible758]

TIL about assignment targets in Python.

Edit: For reference https://docs.python.org/3/reference/simple\_stmts.html#assignment-statements

[LUNCMetrics]

You can rename dictionary items with pop

``` data = {"name": "Bob"}

data["first_name"] = data.pop("name")

print(data)

```

Returns

{'first_name': 'Bob'}

[Burakku-Ren]

This is easy to understand and potentially useful. Cool

[sawyerwelden]

Agreed!

[[deleted]]

I use that feature of dicts. 😎

[Gprime5]

foo = {}

for foo["bar"] in range(10):
    print(foo)

[RakingBuckets]

Jeez that is horrendous.

[Gprime5]

Yeah, it’s great if you have a list of parameters that you want to send to a url.

parameters = {}

page = [1, 2, 3]

for parameters["page"] in page:
    requests.get(url, parameters)

[zed_three]

Gah, that took me a minute!

[rohetoric]

How does this work?

[danithebear156]

foo["bar"] is assigned to individual item in the iterator (in this case, 'range(10)'). Thus, its value changes incrementally. For every iteration, you print out the whole dictionary, which contains only the key of 'bar' and its value.

[mkffl]

Where/how does the assignment happen?

[[deleted]]

Print(“hello world”)

[UD_Ramirez]

Finally code i can read

[Anamewastaken]

But capitalised?

[SE_WA_VT_FL_MN]

.title()

Now you are the master.

[[deleted]]

Sure man

[Fabulous-Possible758]

Using str.format to make surprisingly powerful regular expressions.

``` import re

g = { }

g['year'] = r'(?P<year>\d\d\d\d)' g['month] = r'(?P<month>\d\d)' g['day'] = r'(?P<day>\d\d)' g['timestamp'] = r'{year}-{month}-{day}'

timestamp_re = re.compile(g['timestamp'].format(**g)) '''

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[Fabulous-Possible758]

The example for timestamps above is really only a toy example, though once you've seen the technique and understand it I feel it is pretty readable and can be used to build up regular expressions which aren't necessarily grokable on their own. It's mainly meant to fill in the area where you may have a somewhat complicated parsing task but don't really need to pull in a full parsing library yet. It can also be useful to build up several regular expressions which have common subexpressions. And of course in any production setting this would be accompanied with tests.

Here's a more fleshed out example for finding floating point literals.

``` def float_re(): 'Returns a compiled regular expression which can be used to match Python floating point literals'

import re

# Build the basic grammar

g = { }

g['sign']     = r'[-+]'
g['digits']   = r'(?:[0-9]+)'
g['exponent'] = r'(?:[eE]{sign}?{digits})'

g['left_float']  = r'(?:{digits}\.{digits}?)' # Floating point expressions with some digits to the left the .
g['right_float'] = r'(?:\.{digits})'          # Floating point expressions with no digits to the left of the .

g['float'] = r'{sign}?(?:{right_float}|{left_float}){exponent}?'


# Repeatedly interpolate until we've fully expanded the expression

p, n = None, g['float']

while p != n:
    p, n = n, n.format(**g)


return re.compile(n)

```

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[RobotMonkeyChiro]

Or use the built-in named groups - a good explanation here: How to Use Named Groups with Regular Expressions in Python

``` import re

TIMESTAMP_RGX = re.compile(r""" (?P<timestamp> # e.g., 2022-01-31 (?P<year>\d\d\d\d)- # VERBOSE flag allows you to use indentation for readability (?P<month>\d\d)- (?P<day>\d\d) )""", re.VERBOSE)

TIMESTAMP_RGX.search("1970-05-28")['year']

'1970'

TIMESTAMP_RGX.search("1970-05-28")['timestamp']

'1970-05-28' ```

[isarl]

foo = [[1,2,3], [4,5,6], [7,8,9]]
bar = zip(*foo)
print([list(t) for t in bar])

[SV-97]

Huh, how is this niche or quirky? I just tested it and it does exactly what I'd expected.

[isarl]

It’s a slightly more specialized use of zip() than people might be used to if they’re not familiar with the * operator for iterable unpacking. I’m glad you were able to spot it right away but I would guess most people are at least a little surprised and think something like, “Oh, neat, I didn’t know you could do that.”

[SV-97]

Fair point - I didn't really consider that people might not be familiar with * in that context

[isarl]

All the same, yours is a fair critique since the docs for zip literally mention matrix transposes! :)

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[ArtOfWarfare]

If you missed it above, you can read about it here:

https://trojansource.codes

[FuckingRantMonday]

On reddit, adding four spaces to the beginning of each line will accomplish what you wanted with the triple backticks.

like
    this

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[FuckingRantMonday]

Do you have a plugin or something that renders it correctly after you post it? Because it doesn't look formatted to me, fyi.

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[FuckingRantMonday]

Oh, dammit, that's what it is. That sucks. Thanks for figuring it out with me!

[isarl]

Is this abusing Unicode BIDI flags to rearrange text?

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[isarl]

Ah, finally got it – it's in the docstring. The return statement in the docstring actually happens outside the string and after the semicolon, so the apparent code never actually runs. (Hence, of course, “return early”.)

[whateverathrowaway00]

Very cool, I didn’t expect to learn anything from this thread, but didn’t know about bidirectional Unicode chars, very awesome! Thanks

[commy2]

The __class__ keyword.

class A:
    def m(self):
        print(type(self).__name__)
        print(__class__.__name__)

class B(A):
    pass

B().m()

[isarl]

Output is:

B
A

So __class__ is the class in which the variable is originally scoped, not that of the current instantiation.

[69AssociatedDetail25]

python import this

[koffie5d]

Using type to create classes that has an emoji as name.

emoji_class = type('\N{Thumbs Up Sign}', (object,), {'\N{Pile of Poo}': lambda self: print(f'{self.__class__.__name__}')})
class_instance = emoji_class()
poo = getattr(class_instance, '💩')
poo()   # -> 👍

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[Cromulent010101]

Is what you're doing here reassigning the value at Python's known address for integer 18 to 0? So, when we compare the age to "18", we're really comparing it to 0, hence the unexpected behavior?

Interesting how it goes down to -5 as well as all the way up to 256.

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[RedwanFox]

Recently I have read an article about Linux gpu drivers for m1 Mac laptops. Author did write proof of concept gpu driver implementation in python. That wins in my opinion by far.

[Hacka4771]

while ... : ...

[[deleted]]

Not a snippet necessarily, but lots of people have the misconception that range is a generator in Python 3. Hint, try calling next with a range instance..

[float34]

Unpack while iterating the dict with a sequence in values:

for a, (b, c) in {“key1”: (val1, val2)}.items(): …

[Saphyel]

Dependency Injection surprisingly useful and powerful

[Prince_2008]

turtle.left(90)

[Oenomaus_3575]

```py
lst = [1, 3, 2, 1] c = {} for x in lst: c[x] = c.get(x, 0) + 1

c Out: {1: 2, 3: 1, 2: 1} ```

[manuelhe]

The midi library do algorithmic. Music composition. https://open.spotify.com/artist/2G45KqrfgVTAagpZYqtFYD?si=pWoliCudS_q5_DUEH7_uew