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Contents

cloup.constraints

Constraints for parameter groups.

Submodules

• cloup.constraints.common
• cloup.constraints.conditions
• cloup.constraints.exceptions

Classes summary

If(condition, then[, else_])
AcceptAtMost(n)	Satisfied if the number of set parameters is <= n.
AcceptBetween(min, max)	Satisfied if the number of set parameters is between min and max (included).
And(*constraints)	It’s satisfied if all operands are satisfied.
Constraint()	A constraint that can be checked against an arbitrary collection of CLI parameters with respect to a specific click.Context (which contains the values assigned to the parameters in ctx.params).
Operator(*constraints)	Base class for all n-ary operators defined on constraints.
Or(*constraints)	It’s satisfied if at least one of the operands is satisfied.
Rephraser(constraint[, help, error])	A Constraint decorator that can override the help and/or the error message of the wrapped constraint.
RequireAtLeast(n)	Satisfied if the number of set parameters is >= n.
RequireExactly(n)	Requires an exact number of parameters to be set.
WrapperConstraint(constraint, **attrs)	Abstract class that wraps another constraint and delegates all methods to it.
ConstraintMixin(*args[, constraints, …])	Provides support to constraints.
Equal(param_name, value)	True if the parameter value equals value.
IsSet(param_name)	True if the parameter is set.
Not(predicate)

Functions Summary

constraint(constr, params)

Registers a constraint.

Contents

class cloup.constraints.If(condition: Union[str, Predicate], then: cloup.constraints._core.Constraint, else_: Optional[Constraint] = None)

Bases: cloup.constraints._core.Constraint

A constraint that can be checked against an arbitrary collection of CLI parameters with respect to a specific click.Context (which contains the values assigned to the parameters in ctx.params).

Parameters

• condition (Union[str, cloup.constraints.conditions.Predicate]) –

• then (cloup.constraints._core.Constraint) –

• else_ (Optional[cloup.constraints._core.Constraint]) –

help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__repr__(self) → str

Return repr(self).

class cloup.constraints.AcceptAtMost(n: int)

Bases: cloup.constraints._core.Constraint

Satisfied if the number of set parameters is <= n.

Parameters

n (int) –

help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__repr__(self)

Return repr(self).

class cloup.constraints.AcceptBetween(min: int, max: int)

Bases: cloup.constraints._core.WrapperConstraint

Abstract class that wraps another constraint and delegates all methods to it. Useful when you want to define a parametric constraint combining other existing constraints minimizing the boilerplate.

This is an alternative to defining a function and using Rephraser. Feel free to do that in your code, but cloup will stick to the convention that parametric constraints are defined as classes and written in camel-case.

Parameters

• min (int) –

• max (int) –

help(self, ctx: click.Context) → str

A description of the constraint.

class cloup.constraints.And(*constraints: cloup.constraints._core.Constraint)

Bases: cloup.constraints._core.Operator

It’s satisfied if all operands are satisfied.

Parameters

constraints (cloup.constraints._core.Constraint) –

HELP_SEP =  and

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__and__(self, other) → cloup.constraints._core.And

class cloup.constraints.Constraint

Bases: abc.ABC

A constraint that can be checked against an arbitrary collection of CLI parameters with respect to a specific click.Context (which contains the values assigned to the parameters in ctx.params).

classmethod must_check_consistency(cls) → bool

Returns True if consistency checks are enabled.

classmethod toggle_consistency_checks(cls, value: bool)

Enables/disables consistency checks. Enabling means that:

• check() will call check_consistency()

• ConstraintMixin will call check_consistency on constraints it is responsible for before parsing CLI arguments.

classmethod consistency_checks_toggled(cls, value: bool)

abstract help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

abstract check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

check(self, params: Sequence[Parameter], ctx: Optional[Context] = None) → None

check(self, params: Iterable[str], ctx: Optional[Context] = None) → None

Raises an exception if the constraint is not satisfied by the input parameters in the given (or current) context.

This method calls both check_consistency() (if enabled) and check_values().

Tip

By default check_consistency() is called since it shouldn’t have any performance impact. Nonetheless, you can disable it in production passing False to toggle_consistency_checks().

Parameters

• params – an iterable of parameter names or a sequence of click.Parameter

• ctx – a Context; if not provided, click.get_current_context() is used

Raises

ConstraintViolated UnsatisfiableConstraint

rephrased(self, help: Union[None, str, HelpRephraser] = None, error: Union[None, str, ErrorRephraser] = None) → cloup.constraints._core.Rephraser

hidden(self) → cloup.constraints._core.Rephraser

Hides this constraint from the command help.

__call__(self, param_names: Iterable[str], ctx: Optional[Context] = None) → None

__or__(self, other: cloup.constraints._core.Constraint) → cloup.constraints._core.Or

__and__(self, other: cloup.constraints._core.Constraint) → cloup.constraints._core.And

__repr__(self)

Return repr(self).

class cloup.constraints.Operator(*constraints: cloup.constraints._core.Constraint)

Bases: cloup.constraints._core.Constraint, abc.ABC

Base class for all n-ary operators defined on constraints.

Parameters

constraints (cloup.constraints._core.Constraint) –

HELP_SEP :str

help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

__repr__(self)

Return repr(self).

class cloup.constraints.Or(*constraints: cloup.constraints._core.Constraint)

Bases: cloup.constraints._core.Operator

It’s satisfied if at least one of the operands is satisfied.

Parameters

constraints (cloup.constraints._core.Constraint) –

HELP_SEP =  or

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__or__(self, other) → cloup.constraints._core.Or

class cloup.constraints.Rephraser(constraint: cloup.constraints._core.Constraint, help: Union[None, str, HelpRephraser] = None, error: Union[None, str, ErrorRephraser] = None)

Bases: cloup.constraints._core.Constraint

A Constraint decorator that can override the help and/or the error message of the wrapped constraint.

This is useful also for defining new constraints. See also WrapperConstraint.

Parameters

• constraint (cloup.constraints._core.Constraint) –

• help (Union[None, str, Callable[[click.core.Context, Constraint], str]]) –

• error (Union[None, str, Callable[[click.core.Context, Constraint, Sequence[click.core.Parameter]], str]]) –

help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__repr__(self)

Return repr(self).

class cloup.constraints.RequireAtLeast(n: int)

Bases: cloup.constraints._core.Constraint

Satisfied if the number of set parameters is >= n.

Parameters

n (int) –

help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__repr__(self)

Return repr(self).

class cloup.constraints.RequireExactly(n: int)

Bases: cloup.constraints._core.WrapperConstraint

Requires an exact number of parameters to be set.

Parameters

n (int) –

help(self, ctx: click.Context) → str

A description of the constraint.

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

class cloup.constraints.WrapperConstraint(constraint: cloup.constraints._core.Constraint, **attrs)

Bases: cloup.constraints._core.Constraint

Abstract class that wraps another constraint and delegates all methods to it. Useful when you want to define a parametric constraint combining other existing constraints minimizing the boilerplate.

This is an alternative to defining a function and using Rephraser. Feel free to do that in your code, but cloup will stick to the convention that parametric constraints are defined as classes and written in camel-case.

Parameters

constraint (cloup.constraints._core.Constraint) –

help(self, ctx: click.Context) → str

A description of the constraint.

check_consistency(self, params: Sequence[Parameter]) → None

Performs some sanity checks that detect inconsistencies between this constraints and the properties of the input parameters (e.g. required).

For example, a constraint that requires the parameters to be mutually exclusive is not consistent with a group of parameters with multiple required options.

These sanity checks are meant to catch developer’s mistakes and don’t depend on the values assigned to the parameters; therefore:

• they can be performed before any parameter parsing

• they can be disabled in production (see toggle_consistency_checks())

Parameters

params – list of click.Parameter instances

Raises

UnsatisfiableConstraint if the constraint cannot be satisfied independently from the values provided by the user

check_values(self, params: Sequence[Parameter], ctx: click.Context)

Checks that the constraint is satisfied by the input parameters in the given context, which (among other things) contains the values assigned to the parameters in ctx.params.

You probably don’t want to call this method directly. Use check() instead.

Parameters

• params – list of click.Parameter instances

• ctx – click.Context

Raises

ConstraintViolated

__repr__(self)

Return repr(self).

cloup.constraints.accept_none

cloup.constraints.all_or_none

cloup.constraints.mutually_exclusive

cloup.constraints.require_all

class cloup.constraints.ConstraintMixin(*args, constraints: Sequence[BoundConstraintSpec] = (), show_constraints: bool = False, **kwargs)

Provides support to constraints.

Parameters

• constraints (Sequence[cloup.constraints._support.BoundConstraintSpec]) –

• show_constraints (bool) –

parse_args(self, ctx, args)

get_param_by_name(self, name: str) → click.Parameter

get_params_by_name(self, names: Iterable[str]) → List[Parameter]

format_constraints(self, ctx, formatter) → None

format_help(self, ctx, formatter: click.HelpFormatter) → None

cloup.constraints.constraint(constr: cloup.constraints._core.Constraint, params: Iterable[str])

Registers a constraint.

Parameters

• constr (cloup.constraints._core.Constraint) –

• params (Iterable[str]) –

class cloup.constraints.Equal(param_name: str, value: Any)

Bases: cloup.constraints.conditions.Predicate

True if the parameter value equals value.

Parameters

• param_name (str) –

• value (Any) –

description(self, ctx: click.Context) → str

Succint description of the predicate (alias: desc).

negated_description(self, ctx: click.Context) → str

Succint description of the negation of this predicate (alias: neg_desc).

__call__(self, ctx: click.Context) → bool

Evaluate the predicate on the given context.

class cloup.constraints.IsSet(param_name: str)

Bases: cloup.constraints.conditions.Predicate

A Callable that takes a Context and returns a boolean, with an associated description. Meant to be used as condition in a conditional constraint (see If).

Parameters

param_name (str) –

description(self, ctx: click.Context) → str

Succint description of the predicate (alias: desc).

negated_description(self, ctx: click.Context) → str

Succint description of the negation of this predicate (alias: neg_desc).

__call__(self, ctx: click.Context) → bool

Evaluate the predicate on the given context.

class cloup.constraints.Not(predicate: P)

Bases: cloup.constraints.conditions.Predicate, Generic[P]

A Callable that takes a Context and returns a boolean, with an associated description. Meant to be used as condition in a conditional constraint (see If).

description(self, ctx: click.Context) → str

Succint description of the predicate (alias: desc).

negated_description(self, ctx: click.Context) → str

Succint description of the negation of this predicate (alias: neg_desc).

__call__(self, ctx: click.Context) → bool

Evaluate the predicate on the given context.

__invert__(self) → P

__repr__(self) → str

Return repr(self).

exception cloup.constraints.ConstraintViolated(message: str, ctx: Optional[Context] = None)

Bases: click.UsageError

An internal exception that signals a usage error. This typically aborts any further handling.

Parameters

• message – the error message to display.

• ctx – optionally the context that caused this error. Click will fill in the context automatically in some situations.

classmethod default(cls, params: Iterable[Parameter], desc: str, ctx: Optional[Context] = None) → cloup.constraints.exceptions.ConstraintViolated

exception cloup.constraints.UnsatisfiableConstraint(constraint: cloup.constraints._core.Constraint, params: Iterable[Parameter], reason: str)

Bases: Exception

Raised if a constraint cannot be satisfied by a group of parameters independently from their values at runtime; e.g. mutually_exclusive cannot be satisfied if multiple of the parameters are required.

cloup cloup.constraints.common