[Tutor] What these Python user-defined functions do?

[Max Jegers]

Hi,

I started learning Python (v3.5) and was given some code samples to assist
in my studies. There are some things I could not figure out using Python
documentation or other online sources. I have experience with SQL
programming and some procedural programming, but little in terms of OOP.



I try to slice and dice a Python script that exports a shipment from ERP
system to a text file.

Shipment consists of a Header (H, one record) and Details (D, one or more
records).



Script first imports a library with a number of user-defined functions.
Then the script uses functions defined in library to do exporting to a text
file.

Here is the part of the library:


class View:

def __init__(self):

              self.handle = None

…

def order(self, n):

              return hostviewOrder(handle, self.handle, n)



def put(self, fieldName, value, verify=1):

              if verify == True:

                     verify = 1

              elif verify == False:

                     verify = 0

              return hostviewPut(handle, self.handle, fieldName, value,
verify)



def read(self):

              return hostviewRead(handle, self.handle)



def browse(self, filter="", ascending=1):

              if ascending == True:

                     ascending = 1

              elif ascending == False:

                     ascending = 0

              return hostviewBrowse(handle, self.handle, filter, ascending)



def fetch(self):

              return hostviewFetch(handle, self.handle)



Here is a part of the script I am trying to understand:

def ExportShipment():

         f = open("c:\\" + me.get("SHN") + ".txt", "w")

         h = View("Header", *1*)

         d = View("Details", *1*)

         h.*order*(1) # SHN

         h.*put*("SHN", me.get("SHN"), 1)

         h.*read*()

         f.write("H," + h.get("LOCATION") + "," + h.get("ADDR1") + "\n")

         d.*browse*("SHIUNIQ=" + "{:.0f}".format(h.get("SHIUNIQ")), 1)

         while (d.*fetch*() == 0):

                 f.write("D," + d.get("ITEM") + "," +
"{:.0f}".format(d.get("QTYSHIPPED")) + "\n")

         f.close()



Export output looks like:

H,4,1234 Any Road

D,A2,1

D,B1,3


I understand what file operations do. However I can’t get what these
functions do:

*order(), put(), read(), browse(), fetch()*.


Function definitions in the library are of little help for now, as all
functions feature handle and self.handle in their returns; however I cannot
find out what handle and self.handle may mean in this context.



Please let me know if I should provide more info for my question to make
sense.



Thanks a lot!

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