In boto3, where to put "if" statement to output only values with an empty array?

Question

I am working with aws boto3, still very new to coding & have to find how to drill down my output to only return load balancers/target groups with no target connections.

  def gettargets(arn):
    tglist=elb.describe_target_health(TargetGroupArn=arn)
    targets=[]
    for targetid in tglist["TargetHealthDescriptions"]:
        targets.append(targetid['Target']['Id']) 
    print("Targets:",targets)

elbs = elb.describe_load_balancers(PageSize=100)
for loadbalancer in elbs["LoadBalancers"]:
    print("\n"*2)
    print("-"*8)
    print("ELB Name:",loadbalancer["LoadBalancerName"])
    print("Type:",loadbalancer["Type"])
    print("Scheme:",loadbalancer["Scheme"])
    print("TargetGroups:",str(gettargetgroups(loadbalancer["LoadBalancerArn"])))
    for tgs in gettargetgrouparns(loadbalancer["LoadBalancerArn"]):
     gettargets(tgs)

The Output looks like

    --------
ELB Name: example-elb
Type: application
Scheme: internet-facing
TargetGroups: ['example-tg']
Targets: ['i-09876543210']
    --------
ELB Name: example-alb-2
Type: application
Scheme: internal
TargetGroups: ['example-tg-2']
Targets: []

I need help returning the sections with empty Targets: []

Should I put an if statement in the getargets function or make an if statement for at the bottom. I can sort of read python, and have yet to be able to conceptualize structure and how the pieces work.

Answer 1

You're don't actually 'return' anything here, you just dump results to the screen immediately as you get them.

Split logic and printing and there you have it.

def gettargets(arn):
    tglist=elb.describe_target_health(TargetGroupArn=arn)
    targets=[]
    for targetid in tglist["TargetHealthDescriptions"]:
        targets.append(targetid['Target']['Id']) 
    # now we return, not print!
    return targets



elbs = elb.describe_load_balancers(PageSize=100)
for loadbalancer in elbs["LoadBalancers"]:
    
    targets = []
    for tgs in gettargetgrouparns(loadbalancer["LoadBalancerArn"]):
        targets += gettargets(tgs)

    # print the whole stuff only if targets is empty
    if targets == []:
        print("\n"*2)
        print("-"*8)
        print("ELB Name:",loadbalancer["LoadBalancerName"])
        print("Type:",loadbalancer["Type"])
        print("Scheme:",loadbalancer["Scheme"])
        print("TargetGroups:", str(gettargetgroups( loadbalancer["LoadBalancerArn"])))
        print("Targets:",targets)

Answer 2

You can just return targets from gettargets, and then check if its empty:

  def gettargets(arn):
    tglist=elb.describe_target_health(TargetGroupArn=arn)
    targets=[]
    for targetid in tglist["TargetHealthDescriptions"]:
        targets.append(targetid['Target']['Id']) 
    return targets
    

elbs = elb.describe_load_balancers(PageSize=100)
for loadbalancer in elbs["LoadBalancers"]:
    targets = []
    
    for tgs in gettargetgrouparns(loadbalancer["LoadBalancerArn"]):
       targets += gettargets(tgs)

    if not targets:
        print("\n"*2)
        print("-"*8)
        print("ELB Name:",loadbalancer["LoadBalancerName"])
        print("Type:",loadbalancer["Type"])
        print("Scheme:",loadbalancer["Scheme"])
        print("TargetGroups:",str(gettargetgroups(loadbalancer["LoadBalancerArn"])))
        print("Targets:",  targets)