CODEWITHSUNDEEP
python
jrs11
jrs11

Reputation: 49

Using seek() in Python

I am working on reading specific holter data (.ecg files) and copying specific data, as specified by the user, into a new file. Basically, I only want to read the data into memory that is necessary. Is there a way to use .seek() to only read in data bytes from (start, end)? 

start = args.packet_start
end = args.packet_end

try:

    print("Beginning copying of holter data...")

    # Output the specific holter data
    output_file = open("copied_holter.ecg", 'w')

    # Read part of holter file into memory
    holter = open(args.filename, 'rb')
    data = holter.seek()

# Parse through holter data and copy to file
    for index in range(start, end+1):
    data_list = data[index]
    output_file.write(data_list)

    # Close the file streams
    holter.close()
    output_file.close()  

except Exception as e:
    print(e)
    print("Exiting program, due to exception.")
    exit(1)

print "Finished data copying operations!"

Upvotes: 2

Views: 926

Answers (1)

Muhammad Tahir
Muhammad Tahir

Reputation: 5184

seek will move the pointer to specified location, not return data. read willy return number of bytes specified. Also you should use with statement when working with files or file like objects.

with open(args.filename, 'rb') as holter, open("copied_holter.ecg", 'w') as output_file:
    holter.seek(start)
    data = holter.read(end-start)
    output_file.write(data)

Upvotes: 4

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