RE: [Jython-users] Why is self used so much
by O'Brien-Strain, Eamonn other posts by this author
Feb 28 2002 7:06PM messages near this date
RE: [Jython-users] Example of Java class reloading
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[Jython-users] Trouble with getting to EJB
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The variable "self" is the Python equivalent to Java's "this".
The main differences are:
* In Python you explicitly pass in the "self" parameter to every
(non-static) method, while in Java the "this" value is automatically
available in the methods. (You can think of "this" as being an extra
parameter that is invisibly passed in to each method.)
* In a Java (non-static) method you can refer to an attribute foo
equivalently as either "this.foo" or "foo". In Python however you have to
use "self.foo".
* In Java the name "this" is fixed by the language. In Python the
name "self" is just a programmer convention -- you could use any other name
for the first parameter of methods (but it is not advised because doing so
would confuse other Python programmers)
__
Eamonn O'Brien-Strain
HP Labs
eob@[...].com
-----Original Message-----
From: Martin [mailto:martinb@[...].ie]
Sent: Wednesday, February 27, 2002 9:59 AM
To: jython-users@[...].net
Subject: [Jython-users] Why is self used so much
Hi,
Im new to jython and python but have been programming in java for a while. I
was just wondering why it seems that every variable used has to have self
prefixed to it. A basic applet example of mine is below. This wouldnt
compile/run until self was placed before each variable and between the
brackets of init.
I'd just like to know why this is needed or if im doing something wrong.
from javax.swing import *
from java.awt import *
class Button1(JApplet):
b1 = JButton("Button 1")
b2 = JButton("Butotn 2")
def init(self):
self.cp = self.getContentPane()
self.cp.setLayout(FlowLayout())
self.cp.add(self.b1)
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<DIV> <FONT color=#0000ff face=Arial size=2><SPAN class=954145418-28022002>The
variable "self" is the Python equivalent to Java's "this".</SPAN> </FONT></DIV>
<DIV> <FONT color=#0000ff face=Arial size=2><SPAN
class=954145418-28022002> </SPAN></FONT> </DIV>
<DIV> <FONT color=#0000ff face=Arial size=2><SPAN class=954145418-28022002>The
main differences are:</SPAN> </FONT></DIV>
<UL>
<LI> <FONT color=#0000ff face=Arial size=2><SPAN
class=954145418-28022002> In Python you explicitly pass in the "self"
parameter to every (non-static) method, while in Java the "this" value is
automatically available in the methods. (You can think of "this" as
being an extra parameter that is invisibly passed in to each
method.)</SPAN> </FONT></LI>
<LI> <FONT color=#0000ff face=Arial size=2><SPAN class=954145418-28022002>In a
Java (non-static) method you can refer to an attribute foo equivalently as
either "this.foo" or "foo". In Python however you have to use
"self.foo".</SPAN> </FONT></LI>
<LI> <FONT color=#0000ff face=Arial size=2><SPAN class=954145418-28022002>In
Java the name "this" is fixed by the language. In Python the name "self"
is just a programmer convention -- you could use any other name for the first
parameter of methods (but it is not advised because doing so would confuse
other Python programmers)</SPAN> </FONT></LI></UL>
<DIV> <FONT color=#0000ff face=Arial size=2><SPAN class=954145418-28022002>
<P> <FONT face="Courier New" size=2>__</FONT> <BR><FONT face="Courier New"
size=2> Eamonn O'Brien-Strain</FONT> <BR><FONT face="Courier New" size=2>HP
Labs</FONT> <BR><FONT face="Courier New" size=2>eob@[...].com</FONT>
</P> </SPAN></FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5p
x">
<DIV align=left class=OutlookMessageHeader dir=ltr> <FONT face=Tahoma
size=2> -----Original Message-----<BR><B>From:</B> Martin
[mailto:martinb@[...].ie]<BR> <B>Sent:</B> Wednesday, February 27, 2002 9:59
AM<BR> <B>To:</B> jython-users@[...].net<BR><B>Subject:</B>
[Jython-users] Why is self used so much<BR> <BR></DIV></FONT>
<DIV> <FONT face=Arial size=2><SPAN
class=960425417-27022002> Hi,</SPAN></FONT></DIV>
<DIV> <FONT face=Arial size=2><SPAN class=960425417-27022002>Im new to jython
and python but have been programming in java for a while. I was just wondering
why it seems that every variable used has to have self prefixed to it. A basic
applet example of mine is below. This wouldnt compile/run until self was
placed before each variable and between the brackets of
init.</SPAN> </FONT></DIV>
<DIV> <FONT face=Arial size=2><SPAN class=960425417-27022002>I'd just like to
know why this is needed or if im doing something wrong.</SPAN> </FONT></DIV>
<DIV> <FONT face=Arial size=2><SPAN
class=960425417-27022002> </SPAN></FONT> </DIV>
<DIV> <FONT face=Arial size=2><SPAN class=960425417-27022002>from javax.swing
import *<BR> from java.awt import *</SPAN></FONT></DIV>
<DIV> </DIV>
<DIV> <FONT face=Arial size=2><SPAN class=960425417-27022002> <BR>class
Button1(JApplet):<BR> b1 = JButton("Button 1")<BR> b2 =
JButton("Butotn 2")<BR> def init(self):<BR> self.cp =
self.getContentPane()<BR> self.cp.setLayout(FlowLayout())<BR>
self.cp.add(self.b1)</SPAN> </FONT></DIV></BLOCKQUOTE></BODY></HTML>
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