473,856 Members | 1,834 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

What value should be passed to make a function use the default argument value?

Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..

Thanks in advance.

Oct 3 '06 #1
50 3355
LaundroMat <La*****@gmail. comwrote:
What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..
I don't know if I understand correctly here but:

def f(v=1):
return v * 2

f() returns 2
f(1) returns 2 too

v = 1
f(v) returns 2 too

What do you mean?

--
Lawrence - http://www.oluyede.org/blog
"Nothing is more dangerous than an idea
if it's the only one you have" - E. A. Chartier
Oct 3 '06 #2
LaundroMat wrote:
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()?
f(1)
"None" doesn't seem to work..
None is an object.

</F>

Oct 3 '06 #3
def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..
>>def f(var=1):
.... return var*2
....
>>f()
2
>>f(0.5)
1.0
>>f(123)
246
>>f('hello')
'hellohello'
I'm not sure I follow your problem...what' s stopping you from
passing a value?

-tkc


Oct 3 '06 #4
LaundroMat wrote:
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..

Thanks in advance.
The answer is don't pass any value.

print f()

will print 2

-Larry Bates
Oct 3 '06 #5
On Tue, 03 Oct 2006 13:16:57 -0700, "LaundroMat " <La*****@gmail. comlet
this slip:
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..

Thanks in advance.
a) if you feel that your program needs to pass a value, fix the program.

b)
>>def f(v=1):
.... return v*2
....
>>f()
2
>>f(1)
2
>>f(*[1])
2
>>f(*[])
2
>>>
*[list] is the reverse of def f(*args)

--
Thomas Jollans alias free-zombie
Oct 3 '06 #6
LaundroMat wrote:
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..

What about this?
>>def f(var=None):
.... if var == None:
.... var = 1
.... return 2*var
....
>>f()
2
>>f(3)
6
>>a=4
f(a)
8
>>b=None
f(b)
2
>>>
--Stan Graves

Oct 3 '06 #7
LaundroMat a écrit :
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?

I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..
Have you tried f(1) ?
Oct 3 '06 #8
LaundroMat wrote:
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..
If you *absolutely* want to pass a value and you don't know the default
value (otherwise you could just pass it):
>>import inspect
v = inspect.getargs pec(f)[3][0] # first default value
f(v)
2

Oct 3 '06 #9
On 2006-10-03, LaundroMat <La*****@gmail. comwrote:
Suppose I have this function:

def f(var=1):
return var*2

What value do I have to pass to f() if I want it to evaluate var to 1?
I know that f() will return 2, but what if I absolutely want to pass a
value to f()? "None" doesn't seem to work..

Thanks in advance.
One possible way to do what I think you want is to code as follows:

class Default (object):
pass

def f(var=Default):
if var is Default:
var = 1
return var * 2

--
Antoon Pardon
Oct 4 '06 #10

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

3
8913
by: tornado | last post by:
Hi all, I am pretty new to PHP. I was reading PHP manual and trying out the example from 2nd chapter (A simple Tutorial). When i try to print the variable as given in the example it returns a empty value instead of returning the browser type. Here is the line which i am using in my code and from manual: <?php echo $_SERVER; ?>
3
2846
by: Tito | last post by:
From the Python's tutorial, about default argument values: <quote> The default value is evaluated only once. This makes a difference when the default is a mutable object such as a list, dictionary, or instances of most classes. For example, the following function accumulates the arguments passed to it on subsequent calls: def f(a, L=): L.append(a) return L
20
2576
by: Sam | last post by:
Hi I'm learning to code with C++ and wrote some very simple code. I think it's consistent with every rule but always got compiling errors that I don't understand. The code include 5 files as following, delimited by //////: ////////////////pose.h #ifndef pose_h #define pose_h #include "point.h"
140
7940
by: Oliver Brausch | last post by:
Hello, have you ever heard about this MS-visual c compiler bug? look at the small prog: static int x=0; int bit32() { return ++x; }
21
2258
by: tyler_durden | last post by:
hi there peeps... like I say in the topic, I need to do an e-mail program in C language, and has to be made until the 3th of january..the problem is I'm having some problems with it. I was wondering if someone had a program like this..it has to send e-mails, read e-mails from a .txt file and show them in the screen with the subject, date, etc... can someone please help me out? thanks
23
3662
by: Xah Lee | last post by:
The Concepts and Confusions of Pre-fix, In-fix, Post-fix and Fully Functional Notations Xah Lee, 2006-03-15 Let me summarize: The LISP notation, is a functional notation, and is not a so-called pre-fix notation or algebraic notation. Algebraic notations have the concept of operators, meaning, symbols placed around arguments. In algebraic in-fix notation, different
12
2606
by: dave_dp | last post by:
Hi, I have just started learning C++ language.. I've read much even tried to understand the way standard says but still can't get the grasp of that concept. When parameters are passed/returned by value temporaries are created?(I'm not touching yet the cases where standard allows optimizations from the side of implementations to avoid copying) If so, please quote part of the standard that says that. Assuming it is true, I can imagine two...
4
6703
by: grizggg | last post by:
I have searched and not found an answer to this question. I ran upon the following statement in a *.cpp file in a member function: static const char * const pacz_HTMLContentTypeHeader = "Content-Type: text/html\r\n"; Why is the second const needed and what does it do? Thanks
16
3456
by: John Doe | last post by:
Hi, I wrote a small class to enumerate available networks on a smartphone : class CNetwork { public: CNetwork() {}; CNetwork(CString& netName, GUID netguid): _netname(netName), _netguid(netguid) {}
0
9911
marktang
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
0
9762
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
0
10696
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
1
10780
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
0
10383
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
0
9530
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
1
7932
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
0
5761
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
0
5958
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.