For loop doesn't work inside a python function

Question

I try create a function with a loop for inside. The script work without function but declare the python function don't work. (The original script is is more longer but with this part i think the is enough)

import numpy as np
import math as mt
from sympy import*
import fractions
init_printing(use_latex='mathjax')
PHnumbers=4
PHnumbers2=2
statetype= 1
for d in range(1,9):                                                                                                     
    modes=d+1
    if statetype==1:                                                                                                 
       comb=modes 
    elif statetype==2:
        comb=int((modes*(modes+1))/2)
    exec(f'Phases{d}=[]'), exec(f'Phasesv{d}=[]')
    for i in range(modes):
        exec(f'theta_{i+1}= symbols(\'theta_{i+1}\', real=True)')                                                          
        exec(f'Phases{d}.append(globals()[\'\'.join([\'theta_\',str(i+1)])])') 
        exec(f'Phasesv{d}.append(globals()[\'\'.join([\'theta_\',str(i+1)])])')                                           
        exec(f'v{i+1}=[[0]]*modes')                                                                                        
        exec(f'Phasesv{d}[0]*=0')
    for i in range(modes):
        exec(f'globals()[\'\'.join([\'v\',str(i+1)])][i]=[PHnumbers*diff(Phasesv{d}[i],Phases{d}[i])]')                     
    conteo = d
    for j in range(modes):
        for i in range(modes):
            if j<i:
                conteo = conteo + 1
                exec(f'v{conteo+1}=[[0]]*modes')
                exec(f'globals()[\'\'.join([\'v\',str(conteo+1)])][i]=[PHnumbers2*diff(Phasesv{d}[i],Phases{d}[i])]')  
                exec(f'globals()[\'\'.join([\'v\',str(conteo+1)])][j]=[PHnumbers2*diff(Phasesv{d}[j],Phases{d}[j])]')  
exec(f'Vec{d}=[]'),exec(f'Coeff{d}=[]'), exec(f'Nii{d}=[]'), exec(f'Nij{d}=[]')
for i in range(comb):
        exec(f'Vec{d}.append(globals()[\'\'.join([\'v\',str(i+1)])])')

for i in range(len(Vec4)): print(Vec4[i]) The previous script work, no problems up to here. Now I declare python function:

def metro(PHnumbers):                                                                                                           
    statetype=1
    PHnumbers2=2
    for d in range(1,9):                                                                                                     
        modes=d+1
    if statetype==1:                                                                                                 
        comb=modes 
    elif statetype==2:
        comb=int((modes*(modes+1))/2)
    exec(f'Phases{d}=[]'), exec(f'Phasesv{d}=[]')
    for i in range(modes):
        exec(f'theta_{i+1}= symbols(\'theta_{i+1}\', real=True)')                                                          
        exec(f'Phases{d}.append(globals()[\'\'.join([\'theta_\',str(i+1)])])') 
        exec(f'Phasesv{d}.append(globals()[\'\'.join([\'theta_\',str(i+1)])])')                                           
        exec(f'v{i+1}=[[0]]*modes')                                                                                        
        exec(f'Phasesv{d}[0]*=0')
    for i in range(modes):
        exec(f'globals()[\'\'.join([\'v\',str(i+1)])][i]=[PHnumbers*diff(Phasesv{d}[i],Phases{d}[i])]')                     
    conteo = d
    for j in range(modes):
        for i in range(modes):
            if j<i:
                conteo = conteo + 1
                exec(f'v{conteo+1}=[[0]]*modes')
                exec(f'globals()[\'\'.join([\'v\',str(conteo+1)])][i]=[PHnumbers2*diff(Phasesv{d}[i],Phases{d}[i])]')  
                exec(f'globals()[\'\'.join([\'v\',str(conteo+1)])][j]=[PHnumbers2*diff(Phasesv{d}[j],Phases{d}[j])]')  
exec(f'Vec{d}=[]'),exec(f'Coeff{d}=[]'), exec(f'Nii{d}=[]'), exec(f'Nij{d}=[]')
for i in range(comb):
        exec(f'Vec{d}.append(globals()[\'\'.join([\'v\',str(i+1)])])')
for i in range(len(Vec4)):
    print(Vec4[i])

The second code show problem: 'theta_1 is not defined'

Sorry for an unrelated question, but is this converted from some other prorgamming langauge? — VPfB
– VPfB, Commented Sep 8, 2020 at 7:44
@Italo Can you review your code again and to get indentation correct please? — Nam G VU
– Nam G VU, Commented Sep 8, 2020 at 21:07

Silvio Mayolo · Accepted Answer · 2020-09-08 05:21:11Z

2

From the documentation for exec:

Note: The default locals act as described for function locals() below: modifications to the default locals dictionary should not be attempted. Pass an explicit locals dictionary if you need to see effects of the code on locals after function exec() returns.

So, in essence, you can't use exec to mess with local variables, for interpreter efficiency reasons. The same restriction does not apply to globals, which is why your first version works.

As for what to do: well, the exec calls are highly unnecessary. Simply execute the Python code normally, without the messy exec calls. It'll honestly probably run faster too. In all of the places where you hack together classes of variables with similar names, just replace them with a single array or dictionary, depending on use case.

answered Sep 8, 2020 at 5:21

Silvio Mayolo

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Comments

poproar · Accepted Answer · 2020-09-08 05:22:39Z

2

Looks like it might be an indentation error.

Your first sample is

for d in range(1,9):                                                                                                     
    modes=d+1
    if statetype==1:

while your new definition is

for d in range(1,9):                                                                                                     
    modes=d+1
if statetype==1:

around line 4

answered Sep 8, 2020 at 5:22

poproar

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