Relation:assert
Description
assert all expression
assert exists expression
assert unique expression
assert columns columnlist
Parameters
expression: any valid expression
all: the expression must be true for all rows
exists: the expression must be true for at least one row
unique: the result of the expression unique for all rows
columns: the columns must be present in the relation
columnlist: a comma separated list of valid names
Examples
Using the sample relation films.csv
example | result |
---|---|
assert all director == "Godard" |
Assertion error : all director == "Godard" |
assert exists director == "Godard" |
(passes) |
assert unique year |
Assertion error : unique year |
assert unique director . year |
(passes) |
assert columns film, director |
(passes) |
assert columns film, title |
Assertion error : columns film, title |
Comments
Assert is silent if the test pass. Use assert to check consistency of the data.
Assert does only give a warning, not stop the execution.