141 lines
3.3 KiB
Markdown
141 lines
3.3 KiB
Markdown
---
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Title: Releasing pipe v2.0
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Summary: Introducing partially parametrized pipes!
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---
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# Introducing partially parametrized pipes!
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[pipe](https://github.com/JulienPalard/Pipe) is a very old project of mine, proudly showing 1.3k stars on github!
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I don't maintain it a lot, but today I'm announcing a new release introducing a nice feature: partially parametrized pipes.
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If you're familiar with [currying](https://en.wikipedia.org/wiki/Currying)
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or
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[functools.partial](https://docs.python.org/3/library/functools.html#functools.partial)
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you won't get lost.
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## Show me!
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Before `pipe 2`, the following were already valid:
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```python
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>>> from random import randint
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>>> from pipe import where, sort
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>>>
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>>> negative = where(lambda x: x < 0)
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>>> positive = where(lambda x: x > 0)
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>>>
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>>> numbers = [randint(-10, 10) for _ in range(10)]
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>>>
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>>> numbers | positive | sort
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[7, 10]
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>>> numbers | negative | sort
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[-10, -9, -8, -7, -4, -4, -2]
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```
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It allows to **name things**, naming things make
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code more readable so I wanted more of it.
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It was probably underrated, I like to do this kind of things:
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```python
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>>> isort = sort(key=lambda x: x**2)
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>>> numbers | isort
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[0, -2, -4, -4, -7, 7, -8, -9, 10, -10]
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```
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But it failed as soon as you try go deeper:
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```python
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>>> numbers | isort(reverse=True)
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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File "pipe.py", line 100, in __ror__
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return self.function(other)
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File "pipe.py", line 103, in <lambda>
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return Pipe(lambda x: self.function(x, *args, **kwargs))
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TypeError: Pipe.__call__.<locals>.<lambda>() got an unexpected keyword argument 'reverse'
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```
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Call it a bug, that's what's pipe 2 fixes:
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```python
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>>> from pipe import where, sort
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>>> from random import randint
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>>> numbers = [randint(-10, 10) for _ in range(10)]
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>>>
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>>> isort = sort(key=lambda x: x**2)
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>>> numbers | isort(reverse=True)
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[-10, -9, 8, -6, 6, -4, 4, 4, 2, 1]
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>>>
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```
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Or in the other way around:
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```python
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>>> rsort = sort(reverse=True)
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>>> numbers | rsort
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[8, 6, 4, 4, 2, 1, -4, -6, -9, -10]
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>>> numbers | rsort(key=lambda x: x**2)
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[-10, -9, 8, -6, 6, -4, 4, 4, 2, 1]
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```
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From here you can build many specialized blocks from a single pipe,
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here's a better example:
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```python
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import re
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from pipe import Pipe
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@Pipe
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def grep(iterable, pattern, flags=0, invert=False):
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"""Mimics grep."""
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for line in iterable:
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match = re.match(pattern, line, flags=flags)
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if (match and not invert) or (not match and invert):
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yield line
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```
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Build the small reusable blocks:
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```python
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igrep = grep(flags=re.I)
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vgrep = grep(invert=True)
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vigrep = igrep(invert=True)
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https = igrep("https://")
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not_https = https(invert=True)
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...
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```
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And they all do what you think they do:
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```python
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>>> lines = ["https://python.org", "http://detectportal.firefox.com/", "Just no an URL", "HTTPS://afpy.org"]
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>>> for url in lines | https:
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... print(url)
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...
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https://python.org
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HTTPS://afpy.org
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```
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```python
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>>> for url in lines | not_https:
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... print(url)
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...
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http://detectportal.firefox.com/
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Just no an URL
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```
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Remember I said currying? Yes you can abuse the syntax, but please don't:
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```python
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>>> from pipe import sort
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>>> lines | grep()(invert=True)()(flags=re.I)()("https://")() | sort
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['Just not an URL', 'http://detectportal.firefox.com/']
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```
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As I like to say: « It's not because it's possible that you should do it ».
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