How to check if string consist of consonant, vowel and consonant?

Question

Lets say I have a list of strings verbs = ["win", "dig", "be", "go", "break] etc. I figured out how to duplicate last letter and add "ing" to them. However how can I check if characters in those strings consisting of consonant-vowel-consonat? I have two lists:

vowel = ["a", "e", "i", "o", "u"]
consonant = ["b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "n", "p", "q", "r", "s", "t", "v", "w", "x", "y", "z"]

and here is code sample:

for ver in verbs:
    if verb "I DON'T KNOW WHAT TO TYPE HERE":
        verb = verb[:len(verb)] + verb[len(verb) - 1: len(verb)] + "ing"
        - then do sth

Side note: `verb[:len(verb)]` gives you the whole word, the slice is meaningless; just use `verb` instead. You can use negative numbers in slices, these are automatically subtracted from `len(object)`, and you can *omit* slice components to leave them to the default (being start and end), so `verb[len(verb) - 1: len(verb)]` can be expressed as `verb[-1:]`, or for strings, `verb[-1]` suffices. So it's `verb = verb + verb[-1] + 'ing'`. Or just `verb += verb[-1] + 'ing'` — Martijn Pieters, Jun 18 '18 at 20:58

Martijn Pieters · Accepted Answer · 2018-06-18T21:15:20.570

3

I'd use sets, for fast membership testing:

import string

vowel = set("aeiou")
consonant = set(string.ascii_lowercase) - vowel   # all letters that are not vowels

then just see if those last 3 letters are in the sets:

if len(verb) > 2 and verb[-3] in consonant and verb[-2] in vowel and verb[-1] in consonant:
    verb += verb[-1] + 'ing'

or a little more compact using strict subset testing:

if len(verb) > 2 and {verb[-3], verb[-1]} <= consonant and verb[-2] in vowel:
    verb += verb[-1] + 'ing'

The verb += verb[-1] + 'ing' statement uses augmented assignment to append the last letter plus 'ing' to the verb string value. Negative indices count from the end of the sequence, so -1 gives you the last letter in a string:

>>> verb[-1]
'k'

Demo:

>>> for verb in verbs:
...     if len(verb) > 2 and {verb[-3], verb[-1]} <= consonant and verb[-2] in vowel:
...         verb += verb[-1] + 'ing'
...     else:
...         verb += 'ing'
...     print(verb)
...
winning
digging
being
going
breaking

edited Jun 18 '18 at 21:15

answered Jun 18 '18 at 21:02

Martijn Pieters

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Wouldn't you want verb[0], verb[1] and verb[2]? Negatives would be out of range wouldn't they? – emsimpson92 Jun 18 '18 at 21:03
1

@emsimpson92: because it is the *last 3 characters* that should be tested, not the first three. Negative indices count from the end. – Martijn Pieters Jun 18 '18 at 21:04
I must have missed that specification. – emsimpson92 Jun 18 '18 at 21:04
@emsimpson92: [Here it is](https://docs.python.org/2/reference/expressions.html?highlight=negative#slicings): "If either bound is negative, the sequence’s length is added to it." – Jongware Jun 18 '18 at 21:27

score 1 · Answer 2 · answered Jun 18 '18 at 21:02

I would suggest that use some NLP package like NodeBox or nltk to do this instead of writing custom code to append ing. There might be some case that you may miss.

Some answers here might be helpful:

Using NLTK and WordNet; how do I convert simple tense verb into its present, past or past participle form?

This library is also very helpful https://www.nodebox.net/code/index.php/Linguistics#verb_conjugation

An example:

import en
print en.verb.present_participle("be")

being

How to check if string consist of consonant, vowel and consonant?

2 Answers2