Hex reading problems

I have a huge binary file and I want to quicky edit it with a python script.
I want to search the file for the bytes

Code:

---

54 45 58 30 00 00 20 40 00 00 00 01 FF FF FE E0
00 00 00 40 00 04 CF 44 00 00 00 00 00 80 00 80
00 00 00 0E 00 00 00 01 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

---

or the string

Code:

---

TEX0 @
ÿÿþÃ*@Ã�D€€


---

and replace all the bytes after that to the next occurrence of the string with a different hex file that I want to read in.

I'm having problem reading in these huge (534kb) files. When I say huge I mean to big to edit by hand. I'm not familiar with hex or how its read. The literal string that I copied from my hex editor was turned into that when it looks nothing like that in the actual editor.

Open the file as binary

Code:

---

f = open('filename', 'rwb')
lostString = string # Lost because we are searching for it ;) but seriously this is a list of hex e.g. 0xAB
count = 0
while count != len(lostString):
    if f.read(1) == lostString[count]:
        count += 1
    else:
        count = 0

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This should put you at your byte then you just have to modify that byte and shift the rest of the data down.

Also refrence http://snippets.dzone.com/posts/show/740