Blast parse script: ValueError: Required query and/or hit ID field not found.

Question

[bioinfoSeeker]

Hi, I am trying to write a script to parse and summarize the ncbi web blast output (14 columns). I am using biopython searchIO on the tab delimited output file which is commented by default. I get the error ValueError: Required query and/or hit ID field not found.

I tried to remove the further summarizing openpyxl part of the script and simply run the barebones with searchIO. But the error persists.

file = "out.txt"
blast_generator = SearchIO.parse(file, 'blast-tab', comments=True)
for blast_qresult in blast_generator:
    print blast_qresult
    for k,blast_hit in enumerate(blast_qresult):
        print k
        print blast_hit
        query = blast_qresult.id
        print query

I then tried to repeat the script by adding the column headers exactly and verbatim as present in the blast report.

 custom_fields = 'query id, subject ids, query acc.ver, subject acc.ver, % identity, alignment length, mismatches, gap opens, q. start, q. end, s. start, s. end, evalue, bit score'
 blast_generator = SearchIO.parse(file, 'blast-tab', fields=custom_fields, comments=True)

I still get the same error.

Can you please advice me where I'm going wrong?

[bioinfoSeeker]

In continuation to my post, i'm adding a snippet of my blast report file that I'm trying to parse.

# blastn                                                    
# Iteration: 0                                                  
# Query: 000000577|size:2297896                                                 
# RID: xxxxxx
# Database: nr                                                  
# Fields: query id, subject ids, query acc.ver, subject acc.ver, % identity, alignment length, mismatches, gap opens, q. start, q. end, s. start, s. end, evalue, bit score                                             
# 104 hits found                                                    
000000577|size:2297896  gi|1213423373|gb|CP022124.1|    000000577|size:2297896  CP022124.1  100 252 0   0   1   252 198071  197820  1.30E-127   466
000000577|size:2297896  gi|1213423373|gb|CP022124.1|    000000577|size:2297896  CP022124.1  100 252 0   0   1   252 534111  533860  1.30E-127   466
000000577|size:2297896  gi|1213423373|gb|CP022124.1|    000000577|size:2297896  CP022124.1  100 252 0   0   1   252 725655  725906  1.30E-127   466
000000577|size:2297896  gi|1213423373|gb|CP022124.1|    000000577|size:2297896  CP022124.1  100 252 0   0   1   252 814744  814995  1.30E-127   466
000000577|size:2297896  gi|1213423373|gb|CP022124.1|    000000577|size:2297896  CP022124.1  100 252 0   0   1   252 1178261 1178512 1.30E-127   466
000000577|size:2297896  gi|1188266913|dbj|LC268264.1|   000000577|size:2297896  LC268264.1  100 252 0   0   1   252 156 407 1.30E-127   466
000000577|size:2297896  gi|1188266138|dbj|LC268202.1|   000000577|size:2297896  LC268202.1  100 252 0   0   1   252 156 407 1.30E-127   466
000000577|size:2297896  gi|1188263076|dbj|LC264101.1|   000000577|size:2297896  LC264101.1  100 252 0   0   1   252 156 407 1.30E-127   466
000000577|size:2297896  gi|1188262847|dbj|LC264912.1|   000000577|size:2297896  LC264912.1  100 252 0   0   1   252 156 407 1.30E-127   466

Answer 1

[bioinfoSeeker]

I looked at SearchIO documentation http://biopython.org/DIST/docs/api/Bio.SearchIO.BlastIO-pysrc.html, and used to the table in there to replace the corresponding fields from the blast report, in the script.

custom_fields = 'qseqid, sseqid, qaccver, sacc_ver, nident, length, mismatch, gapopen, qstart, qend, sstart, send, evalue, score'

This still gave the same error. I then remove the commas, and kept the space to see if that helps.

custom_fields = 'qseqid sseqid qaccver sacc_ver nident length mismatch gapopen qstart qend sstart send evalue score'

This resolved the error when printing QueryResult. But I now instead get error "AttributeError: 'Hit' object has no attribute 'sacc_ver' " when I parse this QueryResult and Hit, as the headers now don't match. I will add that error as a separate post.