Limiting number of parameters to a number inputed by the user

April 11, 2022

I am trying to limit the number of parameters defined by the user to the number of inputs first defined by the user in the first input line. nexon = input('Number of exons')

(i.e If the user inputs 2, I want the user to then input values for 2 parameters, ex1 and ex2 if they input 3, I want them to input values for 3 parameters,ex1,ex2,ex3 and so on.) After inputting the parameter values, I’d like to follow the mathematical summation shown below.

Here is the code. I am struggling with why python does not request inputs for ex1, ex2, and so on when it is in an if statement. Is there a way to optimize this using a for loop?

This code only considers the possibility of 4 inputs, ideally I would like it to be able to consider any number of inputs.

The mathematical formula I am trying to incorporate is this one

$IP_{i} = \sum_{j=1}^{i}EL_{j} \mod 3$

nexon = input('Number of exons:')

if nexon == 1:
  ex1 = input("Exon 1 lenght:")
if nexon == 2:
  ex1 = input("Exon 1 lenght:")
  ex2 = input("Exon 2 lenght:")
if nexon == 3:
  ex1 = input("Exon 1 lenght:")
  ex2 = input("Exon 2 lenght:")
  ex3 = input("Exon 3 lenght:")
if nexon == 4:
  ex1 = input("Exon 1 lenght:")
  ex2 = input("Exon 2 lenght:")
  ex3 = input("Exon 3 lenght:")
  ex4 = input("Exon 3 lenght:")

EL1 = int(ex1)
EL2 = int(ex2)
EL3 = int(ex3)
EL4 = int(ex4)

IP1 = (EL1%3)
IP2 = (EL1+EL2)%3
IP3 = (EL1+EL2+EL3)%3
IP4 = (EL1+EL2+EL3+EL4)%3

print('exon 1 phase IP1',IP1)
print('exon 2 phase IP2',IP2)
print('exon 3 phase IP3',IP3)
print('exon 3 phase IP4',IP4)```

>Solution :

You can use a loop to ask for user input repeteadly.

Regarding the modulo calculation, for efficiency you can use numpy:

nexon = int(input('Number of exons:'))

lengths = []
for i in range(nexon):
    lengths.append(int(input(f"Exon {i+1} lenght:")))

import numpy as np

IPs = (np.array(lengths).cumsum()%3).tolist()
    
for i, ip in enumerate(IPs, start=1):
    print(f'exon {i} phase IP{i} {ip}')

example:

Number of exons:4
Exon 1 lenght:1
Exon 2 lenght:3
Exon 3 lenght:5
Exon 4 lenght:8
exon 1 phase IP1 1
exon 2 phase IP2 1
exon 3 phase IP3 0
exon 4 phase IP4 2

python only version:

nexon = int(input('Number of exons:'))

cum_lengths = []
v = 0
for i in range(nexon):
    cum_lengths.append(v+int(input(f"Exon {i+1} lenght:")))
    v = cum_lengths[-1]

IPs = [v%3 for v in cum_lengths]
    
for i, ip in enumerate(IPs, start=1):
    print(f'exon {i} phase IP{i} {ip}')