Develop Reference

What does 'arg1 must be a string, bytes or code object' mean? exec()

an image of the error message for anyone interested
trying to make a simple version of a language translator to a language I made that is similar to one from Outer wilds. but when I try to execute one of the letters for turtle to draw it says as the image above or
arg1 must be a string, bytes or code object
As I am not an amazing coder, I have no clue what that means.
This is the code that I have written and I want to exec()
There is another image containing the code I want to exec()
if anyone can tell me how to solve this thanks! and if you are able to use more simple python and dumb the answer down an little bit so I can understand then that would also be massively helpful!
if you can't dumb it down for me, no problem!

a = T.fd(20)
b = T.fd(20); T.rt(60); T.fd(20)
Neither of those statements does what you think they do. The first statement calls the fd function immediately (presumably moving the turtle forward by 20), and returns None, so None will be stored in a.
The second line also does a forward 20 and stores that return value in b. It then does a right 60 and a forward 20, but nothing about those will be stored in b. Those are completely separate statements.
The bottom line is, if you want to store up a macro to be executed later with exec, then those lines MUST BE STRINGS. You don't have any strings. So, change your code to:
a = "T.fd(20)"
b = "T.fd(20); T.rt(60); T.fd(20)"
...etc...
Then it will do what you want. This is not the BEST way to do this, because exec is a bad habit, but it will do what you want. The better way would be to do something like:
a = "F20"
b = "F20,R60,F20"
and then write a little interpreter to convert those to turtle movements.

max_iters doesn't seem to work with GLPK_MI solver in Python

I'm debugging my code right now and since it's running with some datas and not with other ones, I wanted to set the 'max_iters' option to 1 to see if it works in only 1 iteration or if it needs more. I realised it doesn't seem to even use it. I tried putting a string "hello" instead of an int and it even worked. Do someone knows if it's a known problem?
self.prob.solve(solver="GLPK_MI", max_iters=1)
I'm using the CVXPY module with CVXOPT.
EDIT:
I want to do this because I don't get an error, it just continues to run forever. And with the project I'm working on it can take a lot of time to run so I wonder if it's really not working or if it's just a question of time.

Wouldn't be better if you set the max iterations as a variable? (just a suggestion)
In any case, in CVXOPT you need to set the max number of iteration as
'maxiters' : 1
or you can set it as a variable and then call solver as per below
opts = {'maxiters' : 1}
self.prob.solve(solver="GLPK_MI", options = opts)

Why can't I get the output in Python?

def travel():
travel.s=0
travel.frate=[]
travel.tr=[]
def accomodation():
print"""specialises
1.place 1
a.hotel 1
b.hotel 2
Hotel1:ac/non ac rooms
Ac.for ac...
Noac.for non ac...."""
hd=[5000,6000]
hg=[4000,7000]
TAc=[1000]
Nac=[400]
ch5=input("Enter your choice")
fav=raw_input("ENter hotel choice")
mode=raw_input("Enter ac/no ac")
if(ch5==1):
for i in hd:
frate=hd[i]+TAc
else:
frate=hd[i]+Nac
if(ch5==2):
for i in range(0,2,1):
frate=hg[i]+TAc
else:
frate=hg[i]+Nac
accomodation()
travel()
When i run the program , i get the error as List Index out of range.but in hd and hg list,there are only two elements, so index number will be from 0 right?? Is there anything i should import?? I even gave statements like this:
travel.frate=travel.hg[i]+TAc
but it still doesn't come.Thank you for your effort.
the indentation is proper now,but the output is still not coming.

The specific issue you are encountering is caused by these lines here:
if(ch5==1):
for i in hd:
frate=hd[i]+TAc
hd[i] looks at hd[5000] and hd[6000] which will throw an IndexError.
But if you fix that, you're going to run into another error, because
frate=hd[i]+TAc
tries to add a list TAc to an integer hd[i], which is an unsupported operation. You probably need frate=hd[i]+TAc[0], or even better, make TAc a number rather than a list. This issue occurs elsewhere in your code as well.
Finally, while not causing explicit issues in your code right now, there are two other problems:
ch5=input("Enter your choice") is dangerous since input tells Python to run whatever code snippet the user enters. In this case, much safer to do ch5=int(raw_input("Enter your choice"))
for i in range(0,2,1): is really for i in range(2): - only use the starting index and jump parameters if you need to change them from their default, namely 0 and 1.
There are other issues like variable scope (you're expecting travel.frate to be modified from within accommodation, but that's not happening) and defining variables in functions like travel.frate (not invalid syntax, but definitely strange) but those are probably better addressed outside of this question.

Python: Assert that all objects in a list have a specific attribute values

I am working for a web-app using django-1.6 where there will be application(s) coming in and going through various stages of scrutiny. On satisfying criteria(s), they get approved and promoted to the next stage or get deferred. I was testing the approval transition. And landed up in situation where I need to assert if approvable application(s) have their status changed to pending for the next stage. So, this is how I do it right now:
self.assertEqual('stage2.pending', stage1_approved_mentor_applications[0].status)
what I am looking for is something like
self.assertEqual('stage2.pending', stage1_approved_mentor_applications.status)
which would assure that all the objects in the list stage1_approved_mentor_applications have their status as 'stage2.pending'. One way would be to pass it to a function taking a list and returning True on all status being 'stage2.pending' and False if otherwise. This function will be called in assertTrue. Wondering if there's already a workaround for this that would save me from reinventing the wheel.
Can anyone help me with that? Thanks in advance.

what about this:
for s in stage1_approved_mentor_applications:
self.assertEqual('stage2.pending', s.status)
so you know what status is different

How about this?
self.assertFalse(
any(obj.status != 'stage2.pending' for obj in stage1_approved_mentor_applications)
)

self.assertTrue(
all([x is 'stage2.pending' for x in stage1_approved_mentor_applications]
))

Python - What's the use of if True:?

I just came accross the following code in an existent project, which I'm working on:
if True:
x = 5
y = 6
return x+y
else:
return 'Something
Inside the if True are lots of conditions and some will also return the function already.
Why would somebody write in that way? The code contained some other bugs also, but was just wondering about the if True: statement as it didn't make any sense to me. Probably also pretty stupid to ask it, but was wondering hehe.

It might be a remnant of debugging or refactoring. It may be that instead of True, there was orginally a condition or variable there but it has now been replaced by True. The developer perhaps left it there without refactoring or cleaning it up all the way.
If you're free to edit the code as you wish and you're sure that the else is no longer needed, then you can remove it. It indeed makes no sense to have code in your codebase that will never run.

True doesn't necessarily mean True
True = False
if not True :
print "True is false" # This prints ok
Honestly, I don't think anyone would code like this.

Does not make any sense to me, my guess is that someone wanted to have two distinct code paths that he could alternate between a'la using #if 1 .. #else -> #if 0 ... for debugging or such purposes.
Other possibility was that, as #SimeonVisser suggested, the original developer was refactoring or cleaning up the code (and did not have an emulator that allows one to easily remove 1 step of indentation from a block of code)

It could be a flag used for debugging.

It's simply used to ensure that the else: block is never executed.
I have used if True: for some blocks to ensure that my code really does what I want. Usage for debugging or refactoring.
All in all it makes no real sense to use this in an application but for testing or debugging it's somehow acceptable.