AWS Lambda import module error in python

I am creating a AWS Lambda python deployment package. I am using one external dependency requests . I installed the external dependency using the AWS documentation Below is my python code.

    import requests

    print('Loading function')

    s3 = boto3.client('s3')

    def lambda_handler(event, context):
        #print("Received event: " + json.dumps(event, indent=2))

        # Get the object from the event and show its content type
        bucket = event['Records'][0]['s3']['bucket']['name']
        key = urllib.unquote_plus(event['Records'][0]['s3']['object']['key']).decode('utf8')
            response = s3.get_object(Bucket=bucket, Key=key)
            s3.download_file(bucket,key, '/tmp/data.txt')
            lines = [line.rstrip('\n') for line in open('/tmp/data.txt')]
            for line in lines:
            print("CONTENT TYPE: " + response['ContentType'])
            return response['ContentType']
        except Exception as e:
            print('Error getting object {} from bucket {}. Make sure they exist and your bucket is in the same region as this function.'.format(key, bucket))
            raise e

Created the Zip the content of the project-dir directory and uploaded to the lambda(Zip the directory content, not the directory). When I am execute the function I am getting the below mentioned error.

    START RequestId: 9e64e2c7-d0c3-11e5-b34e-75c7fb49d058 Version: $LATEST
    **Unable to import module 'lambda_function': No module named lambda_function**

    END RequestId: 9e64e2c7-d0c3-11e5-b34e-75c7fb49d058
    REPORT RequestId: 9e64e2c7-d0c3-11e5-b34e-75c7fb49d058  Duration: 19.63 ms  Billed Duration: 100 ms     Memory Size: 128 MB Max Memory Used: 9 MB

Kindly help me to debug the error.

Error was due to file name of the lambda function. While creating the lambda function it will ask for Lambda function handler. You have to name it as your Python_File_Name.Method_Name. In this scenario I named it as lambda.lambda_handler ( is the file name).

Please find below the snapshot. enter image description here