The async version

Setup

Async SDK

model = models[1]
cli = AsyncAnthropic()
prompt = "I'm Jeremy"
m = mk_msg(prompt)
r = await cli.messages.create(messages=[m], model=model, max_tokens=100)
r

Hello, Jeremy! It’s nice to meet you. How are you doing today? Is there something I can help you with or would you just like to chat?

  • id: msg_01H7LKEnvrgPqzzVj4WKqNFZ
  • content: [{'citations': None, 'text': "Hello, Jeremy! It's nice to meet you. How are you doing today? Is there something I can help you with or would you just like to chat?", 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 10, 'output_tokens': 36}
msgs = mk_msgs([prompt, r, "I forgot my name. Can you remind me please?"]) 
msgs
[{'role': 'user', 'content': "I'm Jeremy"},
 {'role': 'assistant',
  'content': [TextBlock(citations=None, text="Hello, Jeremy! It's nice to meet you. How are you doing today? Is there something I can help you with or would you just like to chat?", type='text')]},
 {'role': 'user', 'content': 'I forgot my name. Can you remind me please?'}]
await cli.messages.create(messages=msgs, model=model, max_tokens=200)

You just introduced yourself as Jeremy. That’s your name based on what you told me in your previous message.

  • id: msg_01DDbdY9JsybAT33YowQD9kH
  • content: [{'citations': None, 'text': "You just introduced yourself as Jeremy. That's your name based on what you told me in your previous message.", 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 60, 'output_tokens': 25}

source

AsyncClient

 AsyncClient (model, cli=None, log=False, cache=False)

Async Anthropic messages client.

Exported source 
class AsyncClient(Client):
    def __init__(self, model, cli=None, log=False, cache=False):
        "Async Anthropic messages client."
        super().__init__(model,cli,log,cache)
        if not cli: self.c = AsyncAnthropic(default_headers={'anthropic-beta': 'prompt-caching-2024-07-31'})
c = AsyncClient(model)
c._r(r)
c.use
In: 10; Out: 36; Cache create: 0; Cache read: 0; Total: 46

source

AsyncClient.__call__

 AsyncClient.__call__ (msgs:list, sp='', temp=0, maxtok=4096,
                       maxthinktok=0, prefill='', stream:bool=False,
                       stop=None, tools:Optional[list]=None,
                       tool_choice:Optional[dict]=None, cli=None,
                       log=False, cache=False)

Make an async call to Claude.

Type Default Details
msgs list List of messages in the dialog
sp str The system prompt
temp int 0 Temperature
maxtok int 4096 Maximum tokens
maxthinktok int 0 Maximum thinking tokens
prefill str Optional prefill to pass to Claude as start of its response
stream bool False Stream response?
stop NoneType None Stop sequence
tools Optional None List of tools to make available to Claude
tool_choice Optional None Optionally force use of some tool
cli NoneType None
log bool False
cache bool False
Exported source 
@patch
async def _stream(self:AsyncClient, msgs:list, prefill='', **kwargs):
    async with self.c.messages.stream(model=self.model, messages=mk_msgs(msgs, cache=self.cache), **kwargs) as s:
        if prefill: yield prefill
        async for o in s.text_stream: yield o
        self._log(await s.get_final_message(), prefill, msgs, kwargs)
Exported source 
@patch
@delegates(Client)
async def __call__(self:AsyncClient,
             msgs:list, # List of messages in the dialog
             sp='', # The system prompt
             temp=0, # Temperature
             maxtok=4096, # Maximum tokens
             maxthinktok=0, # Maximum thinking tokens
             prefill='', # Optional prefill to pass to Claude as start of its response
             stream:bool=False, # Stream response?
             stop=None, # Stop sequence
             tools:Optional[list]=None, # List of tools to make available to Claude
             tool_choice:Optional[dict]=None, # Optionally force use of some tool
             **kwargs):
    "Make an async call to Claude."
    if tools: kwargs['tools'] = [get_schema(o) for o in listify(tools)]
    if tool_choice: kwargs['tool_choice'] = mk_tool_choice(tool_choice)
    if maxthinktok: 
        kwargs['thinking']={'type':'enabled', 'budget_tokens':maxthinktok} 
        temp=1; prefill=''
    msgs = self._precall(msgs, prefill, stop, kwargs)
    if any(t == 'image' for t in get_types(msgs)): assert not self.text_only, f"Images are not supported by the current model type: {self.model}"
    if stream: return self._stream(msgs, prefill=prefill, max_tokens=maxtok, system=sp, temperature=temp, **kwargs)
    res = await self.c.messages.create(
        model=self.model, messages=msgs, max_tokens=maxtok, system=sp, temperature=temp, **kwargs)
    return self._log(res, prefill, msgs, maxtok, sp, temp, stream=stream, stop=stop, **kwargs)
c = AsyncClient(model, log=True)
c.use
In: 0; Out: 0; Cache create: 0; Cache read: 0; Total: 0
c.model = models[1]
await c('Hi')

Hello! How can I assist you today? Feel free to ask any questions or let me know what you’d like to discuss.

  • id: msg_019f1ey5xX5icL17v23wEYhU
  • content: [{'citations': None, 'text': "Hello! How can I assist you today? Feel free to ask any questions or let me know what you'd like to discuss.", 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 8, 'output_tokens': 29}
c.use
In: 8; Out: 29; Cache create: 0; Cache read: 0; Total: 37
q = "Concisely, what is the meaning of life?"
pref = 'According to Douglas Adams,'
await c(q, prefill=pref)

According to Douglas Adams, it’s 42. More seriously, the meaning of life is deeply personal and varies across philosophical traditions - from finding happiness, serving others, pursuing knowledge, or creating your own purpose in an inherently meaningless universe. There’s no universal answer, which is perhaps what makes the question so enduring.

  • id: msg_01UySeHLz39g2ub288t2aze4
  • content: [{'citations': None, 'text': "According to Douglas Adams, it's 42. More seriously, the meaning of life is deeply personal and varies across philosophical traditions - from finding happiness, serving others, pursuing knowledge, or creating your own purpose in an inherently meaningless universe. There's no universal answer, which is perhaps what makes the question so enduring.", 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 24, 'output_tokens': 65}
c.use
In: 32; Out: 94; Cache create: 0; Cache read: 0; Total: 126
async for o in await c(q, prefill=pref, stream=True): print(o, end='')
According to Douglas Adams,  it's 42. More seriously, the meaning of life is deeply personal and varies across philosophical traditions - from finding happiness, serving others, pursuing knowledge, or creating your own purpose in an inherently meaningless universe. There's no universal answer, which is perhaps what makes the question so enduring.
c.use
In: 56; Out: 159; Cache create: 0; Cache read: 0; Total: 215
def sums(
    a:int,  # First thing to sum
    b:int=1 # Second thing to sum
) -> int: # The sum of the inputs
    "Adds a + b."
    print(f"Finding the sum of {a} and {b}")
    return a + b
a,b = 604542,6458932
pr = f"What is {a}+{b}?"
sp = "You are a summing expert."
tools=[sums]
choice = mk_tool_choice('sums')
choice
{'type': 'tool', 'name': 'sums'}
msgs = mk_msgs(pr)
r = await c(msgs, sp=sp, tools=tools, tool_choice=choice)
r

ToolUseBlock(id=‘toolu_01TSMw6g94AR6cdyvE3Rtdtb’, input={‘a’: 604542, ‘b’: 6458932}, name=‘sums’, type=‘tool_use’)

  • id: msg_01WgPFTRNN2YrSphkssjTG6j
  • content: [{'id': 'toolu_01TSMw6g94AR6cdyvE3Rtdtb', 'input': {'a': 604542, 'b': 6458932}, 'name': 'sums', 'type': 'tool_use'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: tool_use
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 438, 'output_tokens': 57}

source

mk_funcres_async

 mk_funcres_async (fc, ns)

Given tool use block fc, get tool result, and create a tool_result response.

source

mk_toolres_async

 mk_toolres_async (r:collections.abc.Mapping,
                   ns:Optional[collections.abc.Mapping]=None,
                   obj:Optional=None)

Create a tool_result message from response r.

Type Default Details
r Mapping Tool use request response from Claude
ns Optional None Namespace to search for tools
obj Optional None Class to search for tools 
tr = await mk_toolres_async(r, ns=globals())
tr
Finding the sum of 604542 and 6458932
[{'role': 'assistant',
  'content': [{'id': 'toolu_01TSMw6g94AR6cdyvE3Rtdtb',
    'input': {'a': 604542, 'b': 6458932},
    'name': 'sums',
    'type': 'tool_use'}]},
 {'role': 'user',
  'content': [{'type': 'tool_result',
    'tool_use_id': 'toolu_01TSMw6g94AR6cdyvE3Rtdtb',
    'content': '7063474'}]}]
msgs += tr
r = contents(await c(msgs, sp=sp, tools=sums))
r
'The sum of 604542 and 6458932 is 7,063,474.'

Structured Output

source

AsyncClient.structured

 AsyncClient.structured (msgs:list, tools:Optional[list]=None,
                         obj:Optional=None,
                         ns:Optional[collections.abc.Mapping]=None, sp='',
                         temp=0, maxtok=4096, maxthinktok=0, prefill='',
                         stream:bool=False, stop=None,
                         tool_choice:Optional[dict]=None,
                         metadata:MetadataParam|NotGiven=NOT_GIVEN,
                         stop_sequences:List[str]|NotGiven=NOT_GIVEN, syst
                         em:Union[str,Iterable[TextBlockParam]]|NotGiven=N
                         OT_GIVEN, temperature:float|NotGiven=NOT_GIVEN,
                         thinking:ThinkingConfigParam|NotGiven=NOT_GIVEN,
                         top_k:int|NotGiven=NOT_GIVEN,
                         top_p:float|NotGiven=NOT_GIVEN,
                         extra_headers:Headers|None=None,
                         extra_query:Query|None=None,
                         extra_body:Body|None=None, timeout:float|httpx.Ti
                         meout|None|NotGiven=NOT_GIVEN)

Return the value of all tool calls (generally used for structured outputs)

Type Default Details
msgs list List of messages in the dialog
tools Optional None List of tools to make available to Claude
obj Optional None Class to search for tools
ns Optional None Namespace to search for tools
sp str The system prompt
temp int 0 Temperature
maxtok int 4096 Maximum tokens
maxthinktok int 0 Maximum thinking tokens
prefill str Optional prefill to pass to Claude as start of its response
stream bool False Stream response?
stop NoneType None Stop sequence
tool_choice Optional None Optionally force use of some tool
metadata MetadataParam | NotGiven NOT_GIVEN
stop_sequences List[str] | NotGiven NOT_GIVEN
system Union[str, Iterable[TextBlockParam]] | NotGiven NOT_GIVEN
temperature float | NotGiven NOT_GIVEN
thinking ThinkingConfigParam | NotGiven NOT_GIVEN
top_k int | NotGiven NOT_GIVEN
top_p float | NotGiven NOT_GIVEN
extra_headers Optional None Use the following arguments if you need to pass additional parameters to the API that aren’t available via kwargs.
The extra values given here take precedence over values defined on the client or passed to this method.
extra_query Query | None None
extra_body Body | None None
timeout float | httpx.Timeout | None | NotGiven NOT_GIVEN 
await c.structured(pr, sums)
Finding the sum of 604542 and 6458932
[7063474]
c

ToolUseBlock(id=‘toolu_015qtmiS5yq7JQgxCmjvY6au’, input={‘a’: 604542, ‘b’: 6458932}, name=‘sums’, type=‘tool_use’)

Metric Count Cost (USD)
Input tokens 1,448 0.004344
Output tokens 298 0.004470
Cache tokens 0 0.000000
Total 1,746 $0.008814

AsyncChat

source

AsyncChat

 AsyncChat (model:Optional[str]=None,
            cli:Optional[claudette.core.Client]=None, sp='',
            tools:Optional[list]=None, temp=0, cont_pr:Optional[str]=None,
            cache:bool=False, hist:list=None,
            ns:Optional[collections.abc.Mapping]=None)

Anthropic async chat client.

Type Default Details
model Optional None Model to use (leave empty if passing cli)
cli Optional None Client to use (leave empty if passing model)
sp str
tools Optional None
temp int 0
cont_pr Optional None
cache bool False
hist list None
ns Optional None
Exported source 
@delegates()
class AsyncChat(Chat):
    def __init__(self,
                 model:Optional[str]=None, # Model to use (leave empty if passing `cli`)
                 cli:Optional[Client]=None, # Client to use (leave empty if passing `model`)
                 **kwargs):
        "Anthropic async chat client."
        super().__init__(model, cli, **kwargs)
        if not cli: self.c = AsyncClient(model)
sp = "Never mention what tools you use."
chat = AsyncChat(model, sp=sp)
chat.c.use, chat.h
(In: 0; Out: 0; Cache create: 0; Cache read: 0; Total: 0, [])

source

AsyncChat.__call__

 AsyncChat.__call__ (pr=None, temp=None, maxtok=4096, maxthinktok=0,
                     stream=False, prefill='',
                     tool_choice:Union[str,bool,dict,NoneType]=None, **kw)

Call self as a function.

Type Default Details
pr NoneType None Prompt / message
temp NoneType None Temperature
maxtok int 4096 Maximum tokens
maxthinktok int 0 Maximum thinking tokens
stream bool False Stream response?
prefill str Optional prefill to pass to Claude as start of its response
tool_choice Union None Optionally force use of some tool
kw VAR_KEYWORD
Exported source 
@patch
async def _stream(self:AsyncChat, res):
    async for o in res: yield o
    self.h += mk_toolres(self.c.result, ns=self.tools, obj=self)
Exported source 
@patch
async def _append_pr(self:AsyncChat, pr=None):
    prev_role = nested_idx(self.h, -1, 'role') if self.h else 'assistant' # First message should be 'user' if no history
    if pr and prev_role == 'user': await self()
    self._post_pr(pr, prev_role)
Exported source 
@patch
async def __call__(self:AsyncChat,
                   pr=None,  # Prompt / message
                   temp=None, # Temperature
                   maxtok=4096, # Maximum tokens
                   maxthinktok=0, # Maximum thinking tokens
                   stream=False, # Stream response?
                   prefill='', # Optional prefill to pass to Claude as start of its response
                   tool_choice:Optional[Union[str,bool,dict]]=None, # Optionally force use of some tool
                   **kw):
    if temp is None: temp=self.temp
    await self._append_pr(pr)
    res = await self.c(self.h, stream=stream, prefill=prefill, sp=self.sp, temp=temp, maxtok=maxtok, maxthinktok=maxthinktok, tools=self.tools, tool_choice=tool_choice, **kw)
    if stream: return self._stream(res)
    self.h += await mk_toolres_async(self.c.result, ns=self.ns)
    return res
await chat("I'm Jeremy")
await chat("What's my name?")

Your name is Jeremy, as you mentioned in your previous message.

  • id: msg_011pCCZaehUHEokcUdfw9HBV
  • content: [{'citations': None, 'text': 'Your name is Jeremy, as you mentioned in your previous message.', 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 59, 'output_tokens': 16}
q = "Concisely, what is the meaning of life?"
pref = 'According to Douglas Adams,'
await chat(q, prefill=pref)

According to Douglas Adams, 42. More seriously, the meaning of life is likely what you create through your relationships, pursuits, and values.

  • id: msg_01HnHJXGu96Sz71NCEG5P7mM
  • content: [{'citations': None, 'text': 'According to Douglas Adams, 42. More seriously, the meaning of life is likely what you create through your relationships, pursuits, and values.', 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 95, 'output_tokens': 28}
chat = AsyncChat(model, sp=sp)
async for o in await chat("I'm Jeremy", stream=True): print(o, end='')
Hello Jeremy! It's nice to meet you. How are you doing today? Is there something I can help you with or would you like to chat?
pr = f"What is {a}+{b}?"
chat = AsyncChat(model, sp=sp, tools=[sums])
r = await chat(pr)
r
Finding the sum of 604542 and 6458932

I’ll calculate the sum of those two numbers for you.

  • id: msg_01JwSYNZPzyZz8Dx8F4UYm2B
  • content: [{'citations': None, 'text': "I'll calculate the sum of those two numbers for you.", 'type': 'text'}, {'id': 'toolu_012EnQPvNddWvJoPyeXpozqF', 'input': {'a': 604542, 'b': 6458932}, 'name': 'sums', 'type': 'tool_use'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: tool_use
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 437, 'output_tokens': 85}
pr += " Say the answer in a sentence."
chat = AsyncChat(model, sp=sp, tools=[sums])
r = await chat(pr)
r
Finding the sum of 604542 and 6458932

Let me calculate that sum for you.

  • id: msg_01UCQMWn7W96VEBRUhZrvTJE
  • content: [{'citations': None, 'text': 'Let me calculate that sum for you.', 'type': 'text'}, {'id': 'toolu_01Mdk5rDKjYRxSCKAdgp911d', 'input': {'a': 604542, 'b': 6458932}, 'name': 'sums', 'type': 'tool_use'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: tool_use
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 444, 'output_tokens': 81}
fn = Path('samples/puppy.jpg')
img = fn.read_bytes()
display.Image(img)

q = "In brief, what color flowers are in this image?"
msg = mk_msg([img, q])
await c([msg])

The flowers in the image are purple/lavender in color. They appear to be small daisy-like flowers or asters blooming in the background, while in the foreground there’s an adorable Cavalier King Charles Spaniel puppy (or similar breed) with white and brown fur resting on the grass.

  • id: msg_01Q7ydoG1m2RnRB5gZfcpbyV
  • content: [{'citations': None, 'text': "The flowers in the image are purple/lavender in color. They appear to be small daisy-like flowers or asters blooming in the background, while in the foreground there's an adorable Cavalier King Charles Spaniel puppy (or similar breed) with white and brown fur resting on the grass.", 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 110, 'output_tokens': 71}

Add cache=True to automatically add to Claude’s KV cache. Cache creation tokens are a little more expensive, but cache read tokens are far cheaper.

chat = AsyncChat(model, sp=sp, cache=True)
await chat("Lorem ipsum dolor sit amet" * 150)
chat.use
In: 4; Out: 81; Cache create: 1058; Cache read: 0; Total: 1143

In this followup call, nearly all the tokens are cached, so the only the new additional tokens are charged at the full rate.

await chat("Whoops, sorry about that!")
chat.use
In: 8; Out: 124; Cache create: 1150; Cache read: 1058; Total: 2340

Extended Thinking

Claude 3.7 Sonnet has enhanced reasoning capabilities for complex tasks. See docs for more info.

We can enable extended thinking by passing a thinking param with the following structure.

thinking={
    "type": "enabled",
    "budget_tokens": 16000
}

When extended thinking is enabled a thinking block is included in the response as shown below.

{
  "content": [
    {
      "type": "thinking",
      "thinking": "To approach this, let's think about...",
      "signature": "Imtakcjsu38219c0.eyJoYXNoIjoiYWJjM0NTY3fQ...."
    },
    {
      "type": "text",
      "text": "Yes, there are infinitely many prime numbers such that..."
    }
  ]
}

Let’s call the model without extended thinking enabled.

tk_model = first(has_extended_thinking_models)
chat = AsyncChat(tk_model)
await chat("Write a sentence about Python!")

Python is a versatile programming language known for its readable syntax and wide application in fields ranging from web development to data science and artificial intelligence.

  • id: msg_01E3t5hoTy6zkhpPMQt1vSwU
  • content: [{'citations': None, 'text': 'Python is a versatile programming language known for its readable syntax and wide application in fields ranging from web development to data science and artificial intelligence.', 'type': 'text'}]
  • model: claude-3-7-sonnet-20250219
  • role: assistant
  • stop_reason: end_turn
  • stop_sequence: None
  • type: message
  • usage: {'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'input_tokens': 13, 'output_tokens': 31}

Now, let’s call the model with extended thinking enabled.

r = await chat("Write a sentence about Python!", maxthinktok=1024)
r.content
[ThinkingBlock(signature='ErUBCkYIAxgCIkDwYbWFKH4ZQ5LSZkTNjfHbEYCnHto5D9aeutnOwtJJU2DwMCKNMzK35Yh3KB3DrhHZ0caUCK/6dZAApKCnMz0kEgxc7SfWMEwuZ2+LKzYaDFTsHiFn9/uDsxq7PyIwuhmdrnQe9GjrcZ75auo5nwxegWiHaXyRxXY90JORQBmflZr5FF4YNJZr49tSij8GKh2WfwmADPz3GoCMz4V87aNSMd9EtD0Q5RoONkfkPBgC', thinking="I'm being asked again to write a sentence about Python. Since I've provided two different sentences in my previous responses, I should make sure to write yet another unique sentence about Python to avoid repetition. I'll focus on a different aspect of Python that I haven't mentioned yet, such as its community, ecosystem, history, or specific technical features.", type='thinking'),
 TextBlock(citations=None, text='The robust Python ecosystem boasts thousands of third-party packages that enable developers to quickly build applications without reinventing the wheel, making it one of the most productive programming languages available today.', type='text')]