Pearl Philip - 10 months ago 58

Python Question

I've been trying to get a fix and can't find why the error keeps appearing. Pmin,Pmax,w,fi1 and fi2 have all been assigned finite values

`guess=Pmin+(Pmax-Pmin)*((1-w**2)*fi1+(w**2)*fi2)`

When i remove this line from the code, the same error appears at the next line of code, again for no reason I can think of

Edit: Here is the chunk of code I was referring to:

def Psat(self, T):

`pop= self.getPborder(T)`

boolean=int(pop[0])

P1=pop[1]

P2=pop[2]

if boolean:

Pmin = float(min([P1, P2]))

Pmax = float(max([P1, P2]))

Tr=T/self.typeMolecule.Tc

w=0.5*(1+scipy.tanh((10**5)*(Tr-0.6)))

fi1=0.5*(1-scipy.tanh(8*((Tr**0.4)-1)))

fi2=0.460*scipy.sqrt(1-(Tr-0.566)**2/(0.434**2)+0.494

guess = Pmin+(Pmax-Pmin)*((1-w**2)*fi1+(w**2)*fi2) #error here

solution = scipy.optimize.newton(funcPsat,guess, args=(T,self))

Answer

If you remove the line where the error appears to be and the error moves to the next line, there are two possibilities.

Either *both* lines have a problem or the *previous* line has a problem which is being carried forward.

My bets are on the second option (even more so if you remove another line and it moves again).

For example, the following Python program `twisty_passages.py`

:

```
xyzzy = (1 +
plugh = 7
```

generates the error:

```
File "twisty_passages.py", line 2
plugh = 7
^
SyntaxError: invalid syntax
```

despite the problem clearly being on line 1.

When posting code problems, it's better to give context, such as the five lines immediately before and after where you *think* the error is. You should also post verbatim the error message and any other useful information like a stack trace.

And, now that you *have* posted the code, it appears I was right. The parentheses in the line before where you get your error, is unmatched, very similar to the example I posted:

```
# open parentheses: 1 2 3
fi2=0.460*scipy.sqrt(1-(Tr-0.566)**2/(0.434**2)+0.494
#close parentheses: 1 2
```

Depending on what you're trying to achieve, the solution *may* be as simple as adding another closing parenthesis at the end, to close off the `sqrt`

function.

I can't say for *certain* since I don't recognise the expression off the top of my head. Hardly surprising if it's to do with molecular biology (assuming PSAT is the enzyme, and the use of the `typeMolecule`

identifier) - I seem to recall failing Biology consistently in my youth :-)