Skip to content

Latest commit

 

History

History
147 lines (114 loc) · 5.67 KB

FAQ.md

File metadata and controls

147 lines (114 loc) · 5.67 KB
Raw

FAQ

Contents

I'm running into issues with newlines / complicated statements

You have a couple options here! As mentioned in the README, you can pass in another string to pyp to get a newline. You can also take advantage of features of your shell, such as multiline strings or ANSI C-quoted strings. Let's look at examples!

Passing multiple strings to pyp:

$ pyp --explain 'if int(x) >= 100: x += " is big"; print(x)' 'else: print(x + " is small")'
#!/usr/bin/env python3
import sys
for x in sys.stdin:
    x = x.rstrip('\n')
    if int(x) >= 100:
        x += ' is big'
        print(x)
    else:
        print(x + ' is small')

Using a multiline string:

$ pyp --explain '
> if int(x) >= 100:
>   x += " is big"
>   print(x)
> else:
>   print(x + " is small")
> '

Using an ANSI C-quoted string:

$ pyp --explain $'if int(x) >= 100:\n  x += " is big"\n  print(x)\nelse:\n  print(x + " is small")'

What's in your config?

My config is pretty simple:

import numpy as np

n = int(x)
j = json.loads(stdin)
f = x.split()
# like f, but returns None if index is of bounds
ff = defaultdict(lambda: None, dict(enumerate(x.split())))

d = defaultdict(list)

What are pyp's dependencies?

If run on Python 3.9 or later, pyp has no dependencies.

On earlier Python versions, pyp is dependent on astunparse for --explain/--script to work as promised. Note you can use pyp.py as a Python script without installing astunparse and everything else will work. (In fact --script will still output a script that does what you want it to, but it won't be particularly readable...)

Can I customise the shebang on the output of --script?

Yes! Just add the shebang you want to your config file. pyp will use the shebang of the file pointed to by PYP_CONFIG_PATH as the shebang for the output of --explain/--script.

The output of --explain is a little weirdly formatted

Try running with Python 3.9 or later! The AST unparser that the standard library includes in 3.9 and later fixes a lot of formatting nits that are present in third party AST unparsers.

You can also pipe the output of pyp --explain to an autoformatter like black:

$ pyp --explain x | black --quiet -

What is start up performance like?

It's not perceptible in my use of pyp. And remember that if you're piping input into pyp, processes start in parallel, so this is zero extra wall time if your piped input has any latency.

Here's a benchmark that should basically just be measuring the fixed costs of start up and AST transformation (run on my laptop):

hyperfine -w 10 -m 100 'pyp x'
Benchmark #1: pyp x
  Time (mean ± σ):      56.3 ms ±   1.0 ms    [User: 41.2 ms, System: 11.4 ms]
  Range (min … max):    53.9 ms …  60.3 ms    100 runs

One note here, as mentioned in the README, is that if you use wildcard imports (from x import *) in your config file, pyp might need to perform those imports to resolve undefined names (although pyp avoids this if possible). If this is causing you latency, just import what you need instead (i.e., change your config to read from x import y, z).

What is overall performance like?

Better than awk! ;-)

$ hyperfine -w 3 -m 10 "seq 1 999999 | pyp 'sum(map(int, stdin))'"
Benchmark #1: seq 1 999999 | pyp 'sum(map(int, stdin))'
  Time (mean ± σ):     258.2 ms ±   5.6 ms    [User: 422.3 ms, System: 17.0 ms]
  Range (min … max):   252.1 ms … 270.7 ms    11 runs

$ hyperfine -w 3 -m 10 'seq 1 999999 | awk "{s += $0} END {print s}"'
Benchmark #1: seq 1 999999 | awk "{s += $0} END {print s}"
  Time (mean ± σ):     405.3 ms ±   3.4 ms    [User: 599.6 ms, System: 5.5 ms]
  Range (min … max):   399.4 ms … 410.9 ms    10 runs

More seriously, random micro benchmark aside, pyp should be fast enough that you shouldn't worry about performance until you know you need to, as with Python itself.

One note here is that the the magic variable lines is currently always a list. Hence, if you find yourself processing really large input, it might be better to use the magic variable stdin (this is just sys.stdin). For the above example:

$ hyperfine -w 3 -m 10 "seq 1 999999 | pyp 'sum(map(int, lines))'"
Benchmark #1: seq 1 999999 | pyp 'sum(map(int, lines))'
  Time (mean ± σ):     378.9 ms ±   3.2 ms    [User: 530.2 ms, System: 38.5 ms]
  Range (min … max):   375.4 ms … 384.6 ms    10 runs

Can I use pyp with PyPy?

You should be able to use PyPy! Tests currently pass against PyPy (run tox -e pypy3). You can install pyp using PyPy with something like pypy3 -m pip install pypyp. Running pyp sys.version will tell you whether it worked. Note that pyp requires at least Python 3.8; this constraint naturally applies when using PyPy as well.