Read file content from S3 bucket with boto3

You might consider the smart_open module, which supports iterators:

from smart_open import smart_open

# stream lines from an S3 object
for line in smart_open('s3://mybucket/mykey.txt', 'rb'):
    print(line.decode('utf8'))

and context managers:

with smart_open('s3://mybucket/mykey.txt', 'rb') as s3_source:
    for line in s3_source:
         print(line.decode('utf8'))

    s3_source.seek(0)  # seek to the beginning
    b1000 = s3_source.read(1000)  # read 1000 bytes

Find smart_open at https://pypi.org/project/smart_open/

boto3 offers a resource model that makes tasks like iterating through objects easier. Unfortunately, StreamingBody doesn't provide readline or readlines.

s3 = boto3.resource('s3')
bucket = s3.Bucket('test-bucket')
# Iterates through all the objects, doing the pagination for you. Each obj
# is an ObjectSummary, so it doesn't contain the body. You'll need to call
# get to get the whole body.
for obj in bucket.objects.all():
    key = obj.key
    body = obj.get()['Body'].read()

Using the client instead of resource:

s3 = boto3.client('s3')
bucket='bucket_name'
result = s3.list_objects(Bucket = bucket, Prefix='/something/')
for o in result.get('Contents'):
    data = s3.get_object(Bucket=bucket, Key=o.get('Key'))
    contents = data['Body'].read()
    print(contents.decode("utf-8"))