How to know if ID correspond to nucleotide sequence or protein with a script I have a text file that contains a list of IDs (314 sequences):
AVP78031.1
AVP78042.1
ATO98108.1
ATO98120.1
ATO98132.1
...

My goal is to make a script (maybe using Python or Perl) to check in the list if all the IDs are nucleotide or protein sequences.
For example:
AVP78031.1 -&gt; protein (this is a nucleotide sequence, I change nucleotide for protein to show an example).
AVP78042.1 -&gt; nucleotide
ATO98108.1 -&gt; nucleotide
ATO98120.1 -&gt; nucleotide
ATO98132.1 -&gt; nucleotide

Any idea to do a script?
Thank everybody!
If these are all GenBank or RefSeq accessions, you can use Entrez Direct for this as shown below:
$ cat accs.txt 
ATO98108.1
ATO98120.1
ATO98132.1
AVP78031.1
AVP78042.1
$ cat accs.txt | epost -db nuccore | efetch -format acc
## no output because none of them are nucleotide accessions
$ cat accs.txt | epost -db protein -format acc | efetch -format acc
AVP78042.1
AVP78031.1
ATO98132.1
ATO98120.1
ATO98108.1

NOTE: This will work only if the accessions are currently live because epost does not find any suppressed accessions. For example:
$ cat accs.txt 
NM_002826.3
NM_002826.4
NM_002826.5
$ cat accs.txt | epost -db nuccore -format acc | efetch -format acc
NM_002826.5

Here, all three accessions are valid nucleotide accessions but only the last one, NM_002826.5, is alive.
An alternate way is to use the accession prefixes defined here and come up with an appropriate regular expression query.