Dynamic Values

Several parameters across different prompts accepts callable/function as the argument which allows you to perform additional logic and generate the argument dynamically.

There’s mainly two categories: Before Rendered and After Answered.

Before Rendered

Parameters/Keys in this category will be retrieved before the prompt is displayed in the terminal. The main purpose of this category is to allow Classic Syntax (PyInquirer) users to customise the prompt based on previous prompts result.

When these parameters/keys receive function/callable as an argument, the current InquirerPySessionResult will be provided as an argument and you can perform additional logic to generate and return different values.

Classic Syntax (PyInquirer)

Let’s take the message and default key as an example, in certain scenario, you may want to display different message and obtain different default values based on previous prompts result.

In the following example, the second prompt will set the default value based on the result from the first prompt. And the third prompt will display the message based on the result from second prompt.

from InquirerPy import prompt
from InquirerPy.validator import NumberValidator

def get_message(result):
    return f"Hi {result['confirm_name']}, enter your age:"

questions = [
    {
        "type": "input",
        "message": "Name:",
        "name": "name",
    },
    {
        "type": "input",
        "message": "Confirm Name:",
        "name": 'confirm_name',
        "default": lambda result: result["name"],   # inline lambda to make the code shorter
    },
    {
        "type": "input",
        "message": get_message,   # use a named function for more complex logic
        "name": 'age',
        "validate": NumberValidator(),
    },
]

result = prompt(questions)

Alternate Syntax

When using inquirer, you will receive the result immediately after the prompt execution. Hence you can directly perform your logic to generate the parameters dynamically after each prompt execution.

from InquirerPy import inquirer
from InquirerPy.validator import NumberValidator

name = inquirer.text(message="Name:").execute()
confirm_name = inquirer.text(message="Confirm Name:", default=name).execute()
age_message = f"Hi {confirm_name}, enter your age:"
age = inquirer.text(message=age_message, validate=NumberValidator()).execute()

However for the sake of keeping code shorter and cleaner in certain scenarios, you can also provide applicable parameters with a function/callable.

Attention

To maintain API compatibility with Classic Syntax, the function will also receive an argument, however it will be None. To make your linter/IDE happy, you should put a dummy parameter _ in your function definition.

There are plans in place to remove the need of adding dummy parameter in future.

Note

The following is not a good example that make the code shorter or cleaner..but it just simply illustrate an alternate way of passing arguments.

from InquirerPy import inquirer
from InquirerPy.validator import NumberValidator

name = inquirer.text(message="Name:").execute()
confirm_name = inquirer.text(message="Confirm Name:", default=lambda _:name).execute()
age = inquirer.text(
    message=lambda _: f"Hi {name}, enter your age:", validate=NumberValidator()
).execute()

Parameters/Keys

message

Union[str, Callable[["InquirerPySessionResult"], str]]

Category

Before Rendered

See also

Classic Syntax Example

Alternate Syntax Example

The message parameter/key can either be a simple string or a function which returns string.

default

Union[Any, Callable[["InquirerPySessionResult"], Any]]

Category

Before Rendered

Attention

The default parameter/key typing can vary between different types of prompt.

See also

Classic Syntax Example

Alternate Syntax Example

The default parameter/key can either be a simple value or a function which returns the default value.

choices

Union[List[Any], List["Choice"], List[Dict[str, Any]]]

Category

Before Rendered

Attention

This variable only exists in the following prompts:

  • pages/prompts/list:ListPrompt,

  • pages/prompts/rawlist:RawlistPrompt,

  • pages/prompts/expand:ExpandPrompt,

  • pages/prompts/checkbox:CheckboxPrompt,

  • pages/prompts/fuzzy:FuzzyPrompt

Note

The required keys for choices may vary between prompts. There may be additional keys required which would be documented in individual prompt documentation with additional customised Choice classes.

See also

Separator

Tip

It is recommended to use the Choice class over using dict.

Each choice can be the following types:

  • Any: Any value that have a string representation (e.g. can str(value)).

  • Separator: An instance of the Separator class.

  • dict: Dictionary with the following keys:

    • value (Any): The value of the choice when user selects this choice.

    • name (str): The value that should be presented to the user prior/after selection of the choice.

    • enabled (bool): Indicates if the choice should be pre-selected. This only has effects when the prompt has multiselect enabled.

  • Choice: An instance of the Choice class.

    class InquirerPy.base.control.Choice(value, name=None, enabled=False)[source]

    Class to create choices for list type prompts.

    A simple dataclass that can be used as an alternate to using dict when working with choices.

    Parameters

    • value (Any) – The value of the choice when user selects this choice.

    • name (Optional[str]) – The value that should be presented to the user prior/after selection of the choice. This value is optional, if not provided, it will fallback to the string representation of value.

    • enabled (bool) – Indicates if the choice should be pre-selected. This only has effects when the prompt has multiselect enabled.

    Return type

    None

Classic Syntax (PyInquirer) 
from InquirerPy import prompt
from InquirerPy.base.control import Choice
from InquirerPy.separator import Separator

questions = [
    {
        "type": "list",
        "message": "Select regions:",
        "choices": [
            Choice("ap-southeast-2", name="Sydney"),
            Choice("ap-southeast-1", name="Singapore"),
            Separator(),
            "us-east-1",
            "us-east-2",
        ],
        "multiselect": True,
        "transformer": lambda result: f"{len(result)} region{'s' if len(result) > 1 else ''} selected",
    },
]

result = prompt(questions=questions)
Alternate Syntax 
from InquirerPy import inquirer
from InquirerPy.base.control import Choice
from InquirerPy.separator import Separator

region = inquirer.select(
    message="Select regions:",
    choices=[
        Choice("ap-southeast-2", name="Sydney"),
        Choice("ap-southeast-1", name="Singapore"),
        Separator(),
        "us-east-1",
        "us-east-2",
    ],
    multiselect=True,
    transformer=lambda result: f"{len(result)} region{'s' if len(result) > 1 else ''} selected",
).execute()

After Answered

Parameters/Keys in this category will be retrieved after the question is answered. The main purpose of this category is to allow additional customisation to the appearance of the prompt based on user answer after the prompt is answered.

Parameters/Keys

filter

Callable[[Any], Any]

Category

After Answered

Tip

For prompts that accepts parameter choices, the value provided to the filter function will be the value of the selected choice (choice["value"]) or a list of values of the selected choices.

A function which performs additional transformation on the result. This affects the actual value returned by execute().

Leveraging this parameter/key can potentially shorten the code and create a cleaner code base. Given a scenario you want to obtain the age from the user, however the result from pages/prompts/input:InputPrompt is type of string by default. You can use the filter parameter/key to convert them to int.

Classic Syntax 
from InquirerPy import prompt
from InquirerPy.validator import NumberValidator

questions = [
    {
        "type": "input",
        "message": "Age:",
        "filter": lambda result: int(result),
        "validate": NumberValidator()
    }
]

result = prompt(questions=questions)
Alternate Syntax 
from InquirerPy import inquirer
from InquirerPy.validator import NumberValidator

age = inquirer.text(
    message="Age:", filter=lambda result: int(result), validate=NumberValidator()
).execute()

transformer

Callable[[Any], str]

Category

After Answered

Note

The value received by transformer will always be either type of str or list of str depending on the prompt types.

Tip

filter and transformer run separately and won’t have side effects when running both.

Tip

For prompts that accepts parameter choices, the value provided to the transformer function will be the name of the selected choice (choice["name"]) or a list of names of the selected choices.

A function which performs additional transformation on the value that gets printed to the terminal. Different than filter parameter, this is only visual effect and won’t affect the actual value returned by execute().

For example, when working with pages/prompts/checkbox:CheckboxPrompt, all user selected choices will be displayed in the terminal. This may create unnecessary clutter of texts and may cause the displayed information become less useful. You can use transformer parameter/key to change how the result will be printed.

Classic Syntax 
"""
Without transformer: ? Select regions: ["us-east-1", "us-west-1"]
With transformer: ? Select regions: 2 regions selected
"""
from InquirerPy import prompt
from InquirerPy.base.control import Choice

choices = [
    Choice("ap-southeast-2", name="Sydney", enabled=True),
    Choice("ap-southeast-1", name="Singapore", enabled=False),
    "us-east-1",
    "us-east-2",
]

questions = [
    {
        "type": "checkbox",
        "message": "Select regions:",
        "choices": choices,
        "cycle": False,
        "transformer": lambda result: f"{len(result)} region{'s' if len(result) > 1 else ''} selected",
    }
]

result = prompt(questions=questions)
Alternate Syntax 
"""
Without transformer: ? Select regions: ["us-east-1", "us-west-1"]
With transformer: ? Select regions: 2 regions selected
"""
from InquirerPy import inquirer
from InquirerPy.base.control import Choice

choices = [
    Choice("ap-southeast-2", name="Sydney", enabled=True),
    Choice("ap-southeast-1", name="Singapore", enabled=False),
    "us-east-1",
    "us-east-2",
]

regions = inquirer.checkbox(
    message="Select regions:",
    choices=choices,
    cycle=False,
    transformer=lambda result: f"{len(result)} region{'s' if len(result) > 1 else ''} selected",
).execute()