Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #97819

variable scope of class objects

Show all headers | View raw

Hi,

I've having trouble understanding the self concept as it applies to
variables.  I think I understand how it affects methods.

I haven't been able to fully grasp the scope of class variables and
the effect of the "self"  to the scope of the variable.

I (think) I understand that in the below case, the word self could be
replaced with "BME280" to explicitly call out a variable.

But even still I don't know how explicit call out effects the scope of
a variable.

The below pseudo code is distilled from my 1st attempt at a functional
Python program on the RasPi.

My questions are:
What is the scope of class variables?
does the self. prefix modify this scope?

Thanks

Regards

JonRob




#!/usr/bin/python
# -- developed using Python 2.7.3

class BME280:

# all the below are class variables
# those preceded by an underscore are predefined to some constant
# those without the underscore are to be "working" variables.

    _regT1       = 0x88
    _regH6       = 0xE7
    _coeff_P2    = 0x82
    _coeff_P6    = 0x32
    
    filter       = 0    #should these be "self"?
    t_fine       = 0
    
    def __init__(self, address=0x76, debug=True):
        self.i2c = Adafruit_I2C(address)
        self.address = address
        self.debug = debug
                
    def pressure_calc(self):
        var1 = self.i2c.readU16(self._regT1,False)
        p = (1048576.0 - var1) * _coeff_P2
        return p
        
    def read_pressure(self):      #called  by main application
        pressure_hPa = pressure_calc(self) /10 
        # apply compensation
        return pressure_hPa
                

Back to comp.lang.python | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

variable scope of class objects JonRob - 2015-10-19 14:39 -0400
  Re: variable scope of class objects Random832 <random832@fastmail.com> - 2015-10-19 15:01 -0400
    Re: variable scope of class objects JonRob - 2015-10-20 17:11 -0400
  Re: variable scope of class objects sohcahtoa82@gmail.com - 2015-10-19 16:19 -0700
    Re: variable scope of class objects Terry Reedy <tjreedy@udel.edu> - 2015-10-19 20:03 -0400
  Re: variable scope of class objects Nagy László Zsolt <gandalf@shopzeus.com> - 2015-10-20 07:31 +0200
  Re: variable scope of class objects Luca Menegotto <otlucaDELETE@DELETEyahoo.it> - 2015-10-20 08:17 +0200
    Re: variable scope of class objects Nagy László Zsolt <gandalf@shopzeus.com> - 2015-10-20 08:38 +0200
      Re: variable scope of class objects Luca Menegotto <otlucaDELETE@DELETEyahoo.it> - 2015-10-20 09:23 +0200
    Re: variable scope of class objects JonRob - 2015-10-20 17:33 -0400
      Re: variable scope of class objects Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-10-20 20:18 -0400
        Re: variable scope of class objects JonRob - 2015-10-21 19:35 -0400
          Re: variable scope of class objects Luca Menegotto <otlucaDELETE@DELETEyahoo.it> - 2015-10-22 11:59 +0200
      What does it mean for Python to have “constants”? (was: variable scope of class objects) Ben Finney <ben+python@benfinney.id.au> - 2015-10-21 11:27 +1100
      Re: What does it mean for Python to have “constants”? Nagy László Zsolt <gandalf@shopzeus.com> - 2015-10-21 08:13 +0200
      Re: variable scope of class objects Luca Menegotto <otlucaDELETE@DELETEyahoo.it> - 2015-10-22 07:55 +0200
      Re: variable scope of class objects Erik <python@lucidity.plus.com> - 2015-10-20 23:17 +0100

csiph-web