techniQal support - Latest Comments in Python: Simple File Read and Write

Re: Python: Simple File Read and Write

karuppiah — Thu, 12 Feb 2009 11:24:09 -0000

Hi,
I am opening a file in r+ mode. I have a problem in this. If I first write in a file and then read the same file it is working fine. But some junk characters are added to the end of the string.
Also one more problem if I read it first say using readline function and then write it, the write operation doesn't happen. Any idea what might be the problem?

Re: Python: Simple File Read and Write

shaun — Fri, 19 Dec 2008 10:15:08 -0000

hi, how would you read the whole file in but exclude say the first 4 bytes of it?
thanks
sean

Re: Python: Simple File Read and Write

damniel — Thu, 18 Dec 2008 14:02:52 -0000

Well,
I would argue that the input is a list already. If you are wanting to return a subset of the GeneCode list, I would do the following. There are more graceful ways to achieve this, but this method shows you the logic involved.

x = [0,1,2,3]
GeneCode = ['AAAA','AAAC','AAAG','AAAT']

def Li_to_GC(x):
newList = [GeneCode[i] for i in x]
return newList

print Li_to_GC(x)

In this case, you can then pass any numeric list to LI_to_GC and get the corresponding Genecodes list back.
I would check out this great List comprehension article here, and you can learn more. http://effbot.org/zone/python-list.htm

Re: Python: Simple File Read and Write

Reza — Wed, 17 Dec 2008 14:53:07 -0000

Thank you Daniel, another problem:
x = [0,1,2,3]
GeneCode = ['AAAA','AAAC','AAAG','AAAT']
def Li_to_GC(x):
for i in x:
print GeneCode[i],
Li_to_GC(x)

How can convert the result to the list or string?

Re: Python: Simple File Read and Write

damniel — Fri, 28 Nov 2008 14:55:59 -0000

All you need to do is specify the location of the file you want to save to.

So when opening the second file, specify the directory then.
Example on win32:
file = open("my_dir\\newfile.txt","w")
Example on *nix :
file = open("my_dir/newfile.txt","w")

This will create the new file in the directory "my_dir" assuming the directory exists in the same folder as your python script. You can also specify an absolute file path as well.

Re: Python: Simple File Read and Write

Reza — Fri, 28 Nov 2008 14:04:54 -0000

Hi, I have opened my file I have manipulated and I want save this new change in the other directory. At least I know that I should be use ' r ' for reading and ' w ' command for writing, but I do not know how I can make connection between readings and manipulate file and writing this manipulation in the other file.
Best Regards
Reza _ Finland