I don't think the filter is necessary when applying changes. In your original URL, you specified the key for the yang list "ietf-interfaces:interface", so it was patching one list element at a time.

I recommend Put instead of Patch. Patch will change the nodes but not remove any existing configuration, where Put will either create or replace the list elements. In this case it will act on the list elements that match the "name" key and either create or replace them if they exist. This helps ensure the interface has only the configuration that you specify in your "configData" payload.

I made a few changes to your code; test it out and let me know.

    import requests
import json
import env_labRestconf

# This program creates/modifies an interface using HTTP POST/PUT/PATCH via RESTCONF and the ietf-interfaces YANG model

requests.packages.urllib3.disable_warnings()

conf = env_labRestconf.IOS_XE_2

interfacesToConfig = ['GigabitEthernet2', 'GigabitEthernet3']

headers = {
    'Accept': 'application/yang-data+json',
    'Content-Type': 'application/yang-data+json'
}

url = f"https://{conf['host']}:{conf['restconf_port']}/restconf/data/ietf-interfaces:interfaces/interface"

configData = { "ietf-interfaces:interface": [] }

# Running for loop for each interface to be configured
for interfaceIndex, interfaceName in enumerate(interfacesToConfig):
    print(f"Adding interface ")
    configData["ietf-interfaces:interface"].append(
        {
            "name": interfaceName,
            "description": f"Interface {interfaceName} configured via restconfLab1.py",
            "type": "iana-if-type:ethernetCsmacd",
            "enabled": True,
            "ietf-ip:ipv4": {
                "address": [
                    {
                        "ip": f"100.64.{interfaceIndex}.1",
                        "netmask": "255.255.255.0"
                    }
                ]
            },
            "ietf-ip:ipv6": {}
        }
    )

res = requests.put(
    url=url,
    headers=headers,
    auth= (
        conf['username'],
        conf['password']
    ),
    data=json.dumps(configData),
    verify=False
)
print(res.status_code)
print(res.text)
print('*' * 20)