get()方法非常简单

import botocore
from boto3.session import Session
session = Session(aws_access_key_id='AWS_ACCESS_KEY',
                aws_secret_access_key='AWS_SECRET_ACCESS_KEY')
s3 = session.resource('s3')
bucket_s3 = s3.Bucket('bucket_name')

def not_exist(file_key):
    try:
        file_details = bucket_s3.Object(file_key).get()
        # print(file_details) # This line prints the file details
        return False
    except botocore.exceptions.ClientError as e:
        if e.response['Error']['Code'] == "NoSuchKey": # or you can check with e.reponse['HTTPStatusCode'] == '404'
            return True
        return False # For any other error it's hard to determine whether it exists or not. so based on the requirement feel free to change it to True/ False / raise Exception

print(not_exist('hello_world.txt')) 

我注意到，为了使用botocore.exceptions. clienterror捕获异常，我们需要安装botocore。botocore占用36M的磁盘空间。如果我们使用aws lambda函数，这尤其会产生影响。如果我们只是使用异常，那么我们可以跳过使用额外的库!

我正在验证文件扩展名为'.csv' 如果桶不存在，这将不会抛出异常! 如果桶存在但对象不存在，则不会抛出异常! 如果桶为空，则抛出异常! 如果桶没有权限，就会抛出异常!

代码看起来像这样。请分享你的想法:

import boto3
import traceback

def download4mS3(s3bucket, s3Path, localPath):
    s3 = boto3.resource('s3')

    print('Looking for the csv data file ending with .csv in bucket: ' + s3bucket + ' path: ' + s3Path)
    if s3Path.endswith('.csv') and s3Path != '':
        try:
            s3.Bucket(s3bucket).download_file(s3Path, localPath)
        except Exception as e:
            print(e)
            print(traceback.format_exc())
            if e.response['Error']['Code'] == "404":
                print("Downloading the file from: [", s3Path, "] failed")
                exit(12)
            else:
                raise
        print("Downloading the file from: [", s3Path, "] succeeded")
    else:
        print("csv file not found in in : [", s3Path, "]")
        exit(12)

S3_REGION="eu-central-1"
bucket="mybucket1"
name="objectname"

import boto3
from botocore.client import Config
client = boto3.client('s3',region_name=S3_REGION,config=Config(signature_version='s3v4'))
list = client.list_objects_v2(Bucket=bucket,Prefix=name)
for obj in list.get('Contents', []):
    if obj['Key'] == name: return True
return False

我发现的最简单的方法(可能也是最有效的)是:

import boto3
from botocore.errorfactory import ClientError

s3 = boto3.client('s3')
try:
    s3.head_object(Bucket='bucket_name', Key='file_path')
except ClientError:
    # Not found
    pass

假设您只是想检查一个键是否存在(而不是悄悄地覆盖它)，首先进行这个检查。也会检查错误:

import boto3

def key_exists(mykey, mybucket):
    s3_client = boto3.client('s3')
    try:
        response = s3_client.list_objects_v2(Bucket=mybucket, Prefix=mykey)
        for obj in response['Contents']:
            if mykey == obj['Key']:
                return 'exists'
        return False  # no keys match
    except KeyError:
        return False  # no keys found
    except Exception as e:
        # Handle or log other exceptions such as bucket doesn't exist
        return e

key_check = key_exists('someprefix/myfile-abc123', 'my-bucket-name')
if key_check:
    if key_check == 'exists':
        print("key exists!")
    else:
        print(f"S3 ERROR: {e}")
else:
    print("safe to put new bucket object")
    # try:
    #     resp = s3_client.put_object(Body="Your string or file-like object",
    #                                 Bucket=mybucket,Key=mykey)
    # ...check resp success and ClientError exception for errors...

使用对象。过滤器和检查结果列表是目前为止检查文件是否存在于S3桶中最快的方法。

使用这个简洁的联机程序，当你不得不在一个现有的项目中抛出它而不修改很多代码时，它会减少干扰。

s3_file_exists = lambda filename: bool(list(bucket.objects.filter(Prefix=filename)))

上面的函数假设bucket变量已经声明。

您可以扩展lambda以支持其他参数，例如

s3_file_exists = lambda filename, bucket: bool(list(bucket.objects.filter(Prefix=filename)))