How to replace efficiently a line in huge half ascii half binary file in Python

Question

i need to change the a line in the ascii header of a huge .ply binary file (point cloud format)[see : http://paulbourke.net/dataformats/ply/ ]. I don't need to change anything else.

I'm using python 3.7

i've already been through some solution to replace in text files [How to search and replace text in a file using Python? but neither the Jack Aidley solution's nor jfs solution's match my needs. The first mean to load and rewrite the entire file, which in my case need to be avoided. The second isn't possible with the binary parts of the file.

I need to go from that :

ply
***rest of the header****
property list int int vertex_indices
end_header
^Q(^LI<99><A7> ***rest of the huge binary parts***

to that :

ply
***rest of the header****
property list uchar int vertex_indices
end_header
^Q(^LI<99><A7> ***rest of the huge binary parts***

score 0 · Accepted Answer · answered Jun 12 '19 at 15:00

0

Chances are that sed is up to the task:

sed -e '0,/property list int int vertex_indices/ s/property list int int vertex_indices/property list uchar int vertex_indices/' file

I have routinely replaced strings in binary files (for example Windows .EXE files) without problems.

answered Jun 12 '19 at 15:00

LSerni

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it didn't worked, it just displayed binairies characters – NanBlanc Jun 12 '19 at 15:12
by using `sed -i 's/property list int int vertex_indices/property list uchar int vertex_indices/' file` it worked, thx for the idea – NanBlanc Jun 12 '19 at 15:56

How to replace efficiently a line in huge half ascii half binary file in Python

1 Answers1