update readme file.

Author: varuna-sd

README.md

@@ -8,3 +8,101 @@
 ```bash
 pip install git+git://github.com/SelfHacked/python-stream.git#egg=python-stream
 ```
+
+
+## Usage
+
+### Read file from S3
+
+```python
+from stream.io.s3 import S3ReadFile
+from stream.functions.bytes import un_gzip 
+
+# Read line by line
+with S3ReadFile(bucket='bucket', key='path/to/file.txt.gz', lines=True) as s3_file:
+    for line in un_gzip(s3_file):
+        print(line)
+
+# Read in chunks
+with S3ReadFile(bucket='bucket', key='path/to/file.txt.gz', lines=False) as s3_file:
+    while chunk := s3_file.read(10):
+        print(chunk)
+```
+
+### Upload data to S3
+
+S3WriteFile only uses binary data. Text data should be converted via an encoder before passing to S3WriteFile write methods.
+
+```python
+from stream.io.s3 import S3ReadFile
+from stream.io.s3 import S3WriteFile
+
+# write data to s3 file.
+with S3WriteFile(bucket='bucket', key='path/to/file.txt.gz') as s3_file:
+    s3_file.write(b'test\n')
+    s3_file.writelines([b'line 1\n', b'line 2\n'])
+
+# read from the s3 file.    
+with S3ReadFile(bucket='bucket', key='path/to/file.txt.gz', lines=True) as s3_file:
+    for line in s3_file:
+        print(line)
+```
+
+### Encoding and Decoding
+
+```python
+from stream.functions.bytes import encode, decode
+
+text = [f'line {i}' for i in range(0, 10)]
+
+print('Encoded')
+encoded = encode(text)
+for line in encoded:
+    print(f'   {line}')
+
+print('\nDecoded')
+decoded = decode(encode(text))
+for line in decoded:
+    print(f'   {line}')
+```
+
+
+### Example pipeline
+
+```python
+import gzip
+import csv
+from stream.io.s3 import S3ReadFile, S3WriteFile
+from stream.functions.bytes import encode, decode
+
+# Read from s3 file
+with S3ReadFile('dev-varuna', 'prs/trait1/ss1/data_head.tsv.gz', lines=False) as s3_file:
+    # uncompress
+    gzip_in = gzip.open(s3_file, 'rb')
+    
+    # decode
+    decode_in = decode(gzip_in)
+    
+    # parse the csv row
+    csv_in = csv.reader(decode_in, delimiter='\t')
+
+    # process step (process step should be in iterable format)
+    process = ((line[14], line[12], line[13]) for line in csv_in)
+    
+    # create tsv lines using a generator
+    csv_out = ('\t'.join(line) for line in process)
+    
+    # add new line
+    text_out = (f'{line}\n' for line in csv_out)
+    
+    # encode text lines into bytes
+    encode_out = encode(text_out)
+    
+    # Write to S3
+    with S3WriteFile(
+        'dev-varuna', 'prs/trait1/ss1/snps_custom.tsv.gz',
+    ) as s3_writer, gzip.open(
+        s3_writer, 'wb',
+    ) as gzip_out:
+        gzip_out.writelines(encode_out)
+```