+- Python Forum (https://python-forum.io)
+-- Forum: Python Coding (https://python-forum.io/forum-7.html)
+--- Forum: General Coding Help (https://python-forum.io/forum-8.html)
+--- Thread: Error name 'A' not defined (/thread-21295.html)
Error name 'A' not defined - RavCOder - Sep-23-2019
Hi,
I have this error in my code
Traceback (most recent call last) :
File main.py,line 10 , in <module>
nucleotide = [A,C,G,T]
Error name 'A' not defined
nucleotide = [A,C,G,T]
nucleotide_input= input()
if nucleotide_input != nucleotide:
print("That's not a nucleotide...Try again")
else:
print(nucleotide_input) I don't know how this error don't compile my code , I think that I declared my variable correctly.Regards,
RavCoder
RE: Error name 'A' not defined - ichabod801 - Sep-23-2019
Where did you define A? Not in the code you're showing. Did you perhaps mean to put the string 'A' instead?
RE: Error name 'A' not defined - RavCOder - Sep-23-2019
I wanted to put it like this in such a way that then it makes me the condition that if there was not one of those letters it would print the message to me otherwise I will print the nucleotide.
I will try to put into a string , but I don't know how to do verify if user have inserted the correct value o no .
nucleotide = "ACGT"
RE: Error name 'A' not defined - ichabod801 - Sep-23-2019
Okay, then I would do it this way:
nucleotide = set('ACGT')
nucleotide_input= input()
if nucleotide_input not in nucleotide:
print("That's not a nucleotide...Try again")
else:
print(nucleotide_input) I use the in operator in the if condition. That checks if any of the items in the sequence on the right are equal to the item on the left. I use a set because sets are vary fast at checking the 'in' operator.Here's a subtle twist: if you give set an iterable, it takes each item in the iterable and puts it into the set. A string is an iterable that has characters as items, so each character is put separately into the set. Say you had done this:
if nucleotide_input not in 'ACGT':That would have correctly said 'A', 'C', 'G', and 'T' were nucleotides. But it also would have said 'AC' or 'CGT' was a nucleotide, because the in operator for strings checks for substrings being in the string on the right. By using a set of the individual characters, we only allow 'A', 'C', 'G', and 'T' to be recognized as nucleotides.