PyParsing: Is this correct use of setParseAction()?

2024/9/28 13:21:08

I have strings like this:

"MSE 2110, 3030, 4102"

I would like to output:

[("MSE", 2110), ("MSE", 3030), ("MSE", 4102)]

This is my way of going about it, although I haven't quite gotten it yet:

def makeCourseList(str, location, tokens):print "before: %s" % tokensfor index, course_number in enumerate(tokens[1:]):tokens[index + 1] = (tokens[0][0], course_number)print "after: %s" % tokenscourse = Group(DEPT_CODE + COURSE_NUMBER) # .setResultsName("Course")course_data = (course + ZeroOrMore(Suppress(',') + COURSE_NUMBER)).setParseAction(makeCourseList)

This outputs:

>>> course.parseString("CS 2110")
([(['CS', 2110], {})], {})
>>> course_data.parseString("CS 2110, 4301, 2123, 1110")
before: [['CS', 2110], 4301, 2123, 1110]
after: [['CS', 2110], ('CS', 4301), ('CS', 2123), ('CS', 1110)]
([(['CS', 2110], {}), ('CS', 4301), ('CS', 2123), ('CS', 1110)], {})

Is this the right way to do it, or am I totally off?

Also, the output of isn't quite correct - I want course_data to emit a list of course symbols that are in the same format as each other. Right now, the first course is different from the others. (It has a {}, whereas the others don't.)

Answer

This solution memorizes the department when parsed, and emits a (dept,coursenum) tuple when a number is found.

from pyparsing import Suppress,Word,ZeroOrMore,alphas,nums,delimitedListdata = '''\
MSE 2110, 3030, 4102
CSE 1000, 2000, 3000
'''def memorize(t):memorize.dept = t[0]def token(t):return (memorize.dept,int(t[0]))course = Suppress(Word(alphas).setParseAction(memorize))
number = Word(nums).setParseAction(token)
line = course + delimitedList(number)
lines = ZeroOrMore(line)print lines.parseString(data)

Output:

[('MSE', 2110), ('MSE', 3030), ('MSE', 4102), ('CSE', 1000), ('CSE', 2000), ('CSE', 3000)]
https://en.xdnf.cn/q/71334.html

Related Q&A

Indent and comments in function in Python

I am using Python 2.7 and wrote the following:def arithmetic(A):x=1 """ Some comments here """ if x=1:x=1elif x=2:x=2return 0But it has the indentation issue:if x=1:^ Ind…

Read a large big-endian binary file

I have a very large big-endian binary file. I know how many numbers in this file. I found a solution how to read big-endian file using struct and it works perfect if file is small:data = []file = open(…

SWIG Python Structure Array

Ive been searching for a few days trying to figure out how to turn an array of structures into a Python list. I have a function that returns a pointer to the beginning of the array.struct foo {int memb…

Hashing tuple in Python causing different results in different systems

I was practicing tuple hashing. In there I was working on Python 2.7. Below is the code:num = int(raw_input()) num_list = [int(x) for x in raw_input().split()] print(hash(tuple(num_list)))The above cod…

ctypes pointer into the middle of a numpy array

I know how to get a ctypes pointer to the beginning of a numpy array:a = np.arange(10000, dtype=np.double) p = a.ctypes.data_as(POINTER(c_double)) p.contents c_double(0.0)however, I need to pass the po…

Extracting unsigned char from array of numpy.uint8

I have code to extract a numeric value from a python sequence, and it works well in most cases, but not for a numpy array.When I try to extract an unsigned char, I do the followingunsigned char val = b…

How to hold keys down with pynput?

Im using pynput and I would like to be able to hold keys down, specifically wasd but when I try and run this code it only presses the key and doesnt hold it for 2 seconds. If anyone knows what Im doing…

How well does your language support unicode in practice?

Im looking into new languages, kind of craving for one where I no longer need to worry about charset problems amongst inordinate amounts of other niggles I have with PHP for a new project.I tend to fin…

analogy to scipy.interpolate.griddata?

I want to interpolate a given 3D point cloud:I had a look at scipy.interpolate.griddata and the result is exactly what I need, but as I understand, I need to input "griddata" which means some…

Mongodb TTL expires documents early

I am trying insert a document into a Mongo database and have it automatically expire itself after a predetermine time. So far, my document get inserted but always get deleted from the database from 0 -…