strange syntax error

[al-zatv]

trafficstars

Hello!

Let say I want to calculate frequencies of words in text, and show them in sorted order with their counts. Like:

Input: a b a c a d a d d Output: a 4, d 3, b 1, c 1

I do it this way: $ pyfil -s -l -x 'for ph in f: d[ph]=1+d.get(ph,0)' -e 'for ph in sorted(d, key=d.get)): print(ph,d[ph])'

But, I see an error SyntaxError: invalid syntax (, line 1)

What is wrong here?

[ninjaaron]

The tricky thing is here is that the argument of -e always has to be an expression so it can be printed.

Here's one way to do what you're trying to do:

$ echo "a b a c a d
a d d" | pyfil -s -l -x 'for ph in f: d[ph]=1+d.get(ph,0)' -e 'pair for pair in sorted(d.items(), key=lambda kv: kv[1])'
["b", 1]
["c", 1]
["d", 3]
["a", 4]

When the expression for printing is an iterator (i.e. a lazy iterable) like the generator expression above, it will print each value on a line.

In this specific case, it's easier to simply use a collections.Counter

> echo "a b a c a d
a d d" | pyfil -s -l -x -b "c = collections.Counter()" "c.update(f)" -e "iter(c.most_common())" 
["a", 4]
["d", 3]
["b", 1]
["c", 1]

[al-zatv]

Thank you for explanation and workaround. But,generally speaking, I don't like that generator expressions stuff. Because sometimes instead of simply doing what I want to do, I spend time thinking how to solve that logical puzzle which came from tricky python's syntax. I think it may be more convinient to have an option to write usual python's code in final section, just like in main section. But, it is not necessary, of course.

[ninjaaron]

I'm currently refactoring pyfil to fit my current tastes in code style, and I will keep this feature request in mind.

One of my favorite qualities of pyfil is that it is expression-oriented and tends towards a functional way of expressing computation. However, the feature you're requesting should be simple to implement by simply adding an extra flag, and I don't think it's an unreasonable request.

On the other hand, I do think some of what you're wanting to do sounds like it's near the border where it should just be done in a script or interactively in the REPL---but if you find it practical to use pyfil in this way, I have no problem supporting it.