检查字符串是否包含列表以外的字符串

Question

I have a string as follows:

f = 'ATCTGTCGTYCACGT'

I want to check whether the string contains any characters except: A , C , G or T , and if so, print them.

for i in f:                                                                                                                        
    if i != 'A' and i != 'C' and i != 'G' and i != 'T':                                                                             
        print(i)

Is there a way to achieve this without looping through the string?

Answer 1

Depending on the size of your input string, the for loop might be the most efficient solution.

However, since you explicitly ask for a solution without an explicit loop, this can be done with a regex.

import re

f = 'ABCDEFG'

print(*re.findall('[^ABC]', f), sep='\n')

Outputs

D
E
F
G

Answer 2

You can use set to achieve the desired output.

f = 'ATCTGTCGTYCACGTXYZ'
not_valid={'A', 'C', 'G' , 'T'}
unique=set(f)
print(unique-not_valid)

---

output

{'Y','X','Z'} #characters in f which are not equal to 'A','C','G','T'

Answer 3

Just do

l = ['A', 'C', 'G', 'T']

for i in f:
    if i not in l:
        print(i)

It checks whether the list contains a char of the list

---

If you don't want to loop through the list you can do:

import re

l = ['A', 'C', 'G', 'T']

contains = bool(re.search("%s" % "[" + "".join(l) + "]", f))

Answer 4

Technically this loops but we convert your input string to a set which removes duplicate values

accepted_values = ['a','t','c','g']

input = 'ATCTGTCGTYCACGT'

print([i for i in set(input.lower()) if i not in accepted_values])