CSV::Table

Returns a new CSV::Table object.

• Argument array_of_rows must be an Array of CSV::Row objects.

• Argument headers, if given, may be an Array of Strings.

Create an empty CSV::Table object:

table = CSV::Table.new([])
table # => #<CSV::Table mode:col_or_row row_count:1>

Create a non-empty CSV::Table object:

rows = [
  CSV::Row.new([], []),
  CSV::Row.new([], []),
  CSV::Row.new([], []),
]
table  = CSV::Table.new(rows)
table # => #<CSV::Table mode:col_or_row row_count:4>

If argument headers is an Array of Strings, those Strings become the table’s headers:

table = CSV::Table.new([], headers: ['Name', 'Age'])
table.headers # => ["Name", "Age"]

If argument headers is not given and the table has rows, the headers are taken from the first row:

rows = [
  CSV::Row.new(['Foo', 'Bar'], []),
  CSV::Row.new(['foo', 'bar'], []),
  CSV::Row.new(['FOO', 'BAR'], []),
]
table  = CSV::Table.new(rows)
table.headers # => ["Foo", "Bar"]

If argument headers is not given and the table is empty (has no rows), the headers are also empty:

table  = CSV::Table.new([])
table.headers # => []

Raises an exception if argument array_of_rows is not an Array object:

# Raises NoMethodError (undefined method `first' for :foo:Symbol):
CSV::Table.new(:foo)

Raises an exception if an element of array_of_rows is not a CSV::Table object:

# Raises NoMethodError (undefined method `headers' for :foo:Symbol):
CSV::Table.new([:foo])

If row_or_array is a CSV::Row object, it is appended to the table:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table << CSV::Row.new(table.headers, ['bat', 3])
table[3] # => #<CSV::Row "Name":"bat" "Value":3>

If row_or_array is an Array, it is used to create a new CSV::Row object which is then appended to the table:

table << ['bam', 4]
table[4] # => #<CSV::Row "Name":"bam" "Value":4>

Returns true if all each row of self == the corresponding row of other_table, otherwise, false.

The access mode does no affect the result.

Equal tables:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
other_table = CSV.parse(source, headers: true)
table == other_table # => true

Different row count:

other_table.delete(2)
table == other_table # => false

Different last row:

other_table << ['bat', 3]
table == other_table # => false

Returns data from the table; does not modify the table.

Fetch a Row by Its Integer Index

• Form: table[n], n an integer.

• Access mode: :row or :col_or_row.

• Return value: nth row of the table, if that row exists; otherwise nil.

Returns the nth row of the table if that row exists:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_row! # => #<CSV::Table mode:row row_count:4>
table[1] # => #<CSV::Row "Name":"bar" "Value":"1">
table.by_col_or_row! # => #<CSV::Table mode:col_or_row row_count:4>
table[1] # => #<CSV::Row "Name":"bar" "Value":"1">

Counts backward from the last row if n is negative:

table[-1] # => #<CSV::Row "Name":"baz" "Value":"2">

Returns nil if n is too large or too small:

table[4] # => nil
table[-4] # => nil

Raises an exception if the access mode is :row and n is not an Integer:

table.by_row! # => #<CSV::Table mode:row row_count:4>
# Raises TypeError (no implicit conversion of String into Integer):
table['Name']

Fetch a Column by Its Integer Index

• Form: table[n], n an Integer.

• Access mode: :col.

• Return value: nth column of the table, if that column exists; otherwise an Array of nil fields of length self.size.

Returns the nth column of the table if that column exists:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_col! # => #<CSV::Table mode:col row_count:4>
table[1] # => ["0", "1", "2"]

Counts backward from the last column if n is negative:

table[-2] # => ["foo", "bar", "baz"]

Returns an Array of nil fields if n is too large or too small:

table[4] # => [nil, nil, nil]
table[-4] # => [nil, nil, nil]

Fetch Rows by Range

• Form: table[range], range a Range object.

• Access mode: :row or :col_or_row.

• Return value: rows from the table, beginning at row range.start, if those rows exists.

Returns rows from the table, beginning at row range.first, if those rows exist:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_row! # => #<CSV::Table mode:row row_count:4>
rows = table[1..2] # => #<CSV::Row "Name":"bar" "Value":"1">
rows # => [#<CSV::Row "Name":"bar" "Value":"1">, #<CSV::Row "Name":"baz" "Value":"2">]
table.by_col_or_row! # => #<CSV::Table mode:col_or_row row_count:4>
rows = table[1..2] # => #<CSV::Row "Name":"bar" "Value":"1">
rows # => [#<CSV::Row "Name":"bar" "Value":"1">, #<CSV::Row "Name":"baz" "Value":"2">]

If there are too few rows, returns all from range.start to the end:

rows = table[1..50] # => #<CSV::Row "Name":"bar" "Value":"1">
rows # => [#<CSV::Row "Name":"bar" "Value":"1">, #<CSV::Row "Name":"baz" "Value":"2">]

Special case: if range.start == table.size, returns an empty Array:

table[table.size..50] # => []

If range.end is negative, calculates the ending index from the end:

rows = table[0..-1]
rows # => [#<CSV::Row "Name":"foo" "Value":"0">, #<CSV::Row "Name":"bar" "Value":"1">, #<CSV::Row "Name":"baz" "Value":"2">]

If range.start is negative, calculates the starting index from the end:

rows = table[-1..2]
rows # => [#<CSV::Row "Name":"baz" "Value":"2">]

If range.start is larger than table.size, returns nil:

table[4..4] # => nil

Fetch Columns by Range

• Form: table[range], range a Range object.

• Access mode: :col.

• Return value: column data from the table, beginning at column range.start, if those columns exist.

Returns column values from the table, if the column exists; the values are arranged by row:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_col!
table[0..1] # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]

Special case: if range.start == headers.size, returns an Array (size: table.size) of empty Arrays:

table[table.headers.size..50] # => [[], [], []]

If range.end is negative, calculates the ending index from the end:

table[0..-1] # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]

If range.start is negative, calculates the starting index from the end:

table[-2..2] # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]

If range.start is larger than table.size, returns an Array of nil values:

table[4..4] # => [nil, nil, nil]

Fetch a Column by Its String Header

• Form: table[header], header a String header.

• Access mode: :col or :col_or_row

• Return value: column data from the table, if that header exists.

Returns column values from the table, if the column exists:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_col! # => #<CSV::Table mode:col row_count:4>
table['Name'] # => ["foo", "bar", "baz"]
table.by_col_or_row! # => #<CSV::Table mode:col_or_row row_count:4>
col = table['Name']
col # => ["foo", "bar", "baz"]

Modifying the returned column values does not modify the table:

col[0] = 'bat'
col # => ["bat", "bar", "baz"]
table['Name'] # => ["foo", "bar", "baz"]

Returns an Array of nil values if there is no such column:

table['Nosuch'] # => [nil, nil, nil]

Puts data onto the table.

Set a Row by Its Integer Index

• Form: table[n] = row, n an Integer, row a CSV::Row instance or an Array of fields.

• Access mode: :row or :col_or_row.

• Return value: row.

If the row exists, it is replaced:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
new_row = CSV::Row.new(['Name', 'Value'], ['bat', 3])
table.by_row! # => #<CSV::Table mode:row row_count:4>
return_value = table[0] = new_row
return_value.equal?(new_row) # => true # Returned the row
table[0].to_h # => {"Name"=>"bat", "Value"=>3}

With access mode :col_or_row:

table.by_col_or_row! # => #<CSV::Table mode:col_or_row row_count:4>
table[0] = CSV::Row.new(['Name', 'Value'], ['bam', 4])
table[0].to_h # => {"Name"=>"bam", "Value"=>4}

With an Array instead of a CSV::Row, inherits headers from the table:

array = ['bad', 5]
return_value = table[0] = array
return_value.equal?(array) # => true # Returned the array
table[0].to_h # => {"Name"=>"bad", "Value"=>5}

If the row does not exist, extends the table by adding rows: assigns rows with nil as needed:

table.size # => 3
table[5] = ['bag', 6]
table.size # => 6
table[3] # => nil
table[4]# => nil
table[5].to_h # => {"Name"=>"bag", "Value"=>6}

Note that the nil rows are actually nil, not a row of nil fields.

Set a Column by Its Integer Index

• Form: table[n] = array_of_fields, n an Integer, array_of_fields an Array of String fields.

• Access mode: :col.

• Return value: array_of_fields.

If the column exists, it is replaced:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
new_col = [3, 4, 5]
table.by_col! # => #<CSV::Table mode:col row_count:4>
return_value = table[1] = new_col
return_value.equal?(new_col) # => true # Returned the column
table[1] # => [3, 4, 5]
# The rows, as revised:
table.by_row! # => #<CSV::Table mode:row row_count:4>
table[0].to_h # => {"Name"=>"foo", "Value"=>3}
table[1].to_h # => {"Name"=>"bar", "Value"=>4}
table[2].to_h # => {"Name"=>"baz", "Value"=>5}
table.by_col! # => #<CSV::Table mode:col row_count:4>

If there are too few values, fills with nil values:

table[1] = [0]
table[1] # => [0, nil, nil]

If there are too many values, ignores the extra values:

table[1] = [0, 1, 2, 3, 4]
table[1] # => [0, 1, 2]

If a single value is given, replaces all fields in the column with that value:

table[1] = 'bat'
table[1] # => ["bat", "bat", "bat"]

Set a Column by Its String Header

• Form: table[header] = field_or_array_of_fields, header a String header, field_or_array_of_fields a field value or an Array of String fields.

• Access mode: :col or :col_or_row.

• Return value: field_or_array_of_fields.

If the column exists, it is replaced:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
new_col = [3, 4, 5]
table.by_col! # => #<CSV::Table mode:col row_count:4>
return_value = table['Value'] = new_col
return_value.equal?(new_col) # => true # Returned the column
table['Value'] # => [3, 4, 5]
# The rows, as revised:
table.by_row! # => #<CSV::Table mode:row row_count:4>
table[0].to_h # => {"Name"=>"foo", "Value"=>3}
table[1].to_h # => {"Name"=>"bar", "Value"=>4}
table[2].to_h # => {"Name"=>"baz", "Value"=>5}
table.by_col! # => #<CSV::Table mode:col row_count:4>

If there are too few values, fills with nil values:

table['Value'] = [0]
table['Value'] # => [0, nil, nil]

If there are too many values, ignores the extra values:

table['Value'] = [0, 1, 2, 3, 4]
table['Value'] # => [0, 1, 2]

If the column does not exist, extends the table by adding columns:

table['Note'] = ['x', 'y', 'z']
table['Note'] # => ["x", "y", "z"]
# The rows, as revised:
table.by_row!
table[0].to_h # => {"Name"=>"foo", "Value"=>0, "Note"=>"x"}
table[1].to_h # => {"Name"=>"bar", "Value"=>1, "Note"=>"y"}
table[2].to_h # => {"Name"=>"baz", "Value"=>2, "Note"=>"z"}
table.by_col!

If a single value is given, replaces all fields in the column with that value:

table['Value'] = 'bat'
table['Value'] # => ["bat", "bat", "bat"]

Returns a duplicate of self, in column mode (see Column Mode):

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.mode # => :col_or_row
dup_table = table.by_col
dup_table.mode # => :col
dup_table.equal?(table) # => false # It's a dup

This may be used to chain method calls without changing the mode (but also will affect performance and memory usage):

dup_table.by_col['Name']

Also note that changes to the duplicate table will not affect the original.

Sets the mode for self to column mode (see Column Mode); returns self:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.mode # => :col_or_row
table1 = table.by_col!
table.mode # => :col
table1.equal?(table) # => true # Returned self

Returns a duplicate of self, in mixed mode (see Mixed Mode):

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true).by_col!
table.mode # => :col
dup_table = table.by_col_or_row
dup_table.mode # => :col_or_row
dup_table.equal?(table) # => false # It's a dup

This may be used to chain method calls without changing the mode (but also will affect performance and memory usage):

dup_table.by_col_or_row['Name']

Also note that changes to the duplicate table will not affect the original.

Sets the mode for self to mixed mode (see Mixed Mode); returns self:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true).by_col!
table.mode # => :col
table1 = table.by_col_or_row!
table.mode # => :col_or_row
table1.equal?(table) # => true # Returned self

Returns a duplicate of self, in row mode (see Row Mode):

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.mode # => :col_or_row
dup_table = table.by_row
dup_table.mode # => :row
dup_table.equal?(table) # => false # It's a dup

This may be used to chain method calls without changing the mode (but also will affect performance and memory usage):

dup_table.by_row[1]

Also note that changes to the duplicate table will not affect the original.

Sets the mode for self to row mode (see Row Mode); returns self:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.mode # => :col_or_row
table1 = table.by_row!
table.mode # => :row
table1.equal?(table) # => true # Returned self

If the access mode is :row or :col_or_row, and each argument is either an Integer or a Range, returns deleted rows. Otherwise, returns deleted columns data.

In either case, the returned values are in the order specified by the arguments. Arguments may be repeated.

Returns rows as an Array of CSV::Row objects.

One index:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
deleted_values = table.delete(0)
deleted_values # => [#<CSV::Row "Name":"foo" "Value":"0">]

Two indexes:

table = CSV.parse(source, headers: true)
deleted_values = table.delete(2, 0)
deleted_values # => [#<CSV::Row "Name":"baz" "Value":"2">, #<CSV::Row "Name":"foo" "Value":"0">]

Returns columns data as column Arrays.

One header:

table = CSV.parse(source, headers: true)
deleted_values = table.delete('Name')
deleted_values # => ["foo", "bar", "baz"]

Two headers:

table = CSV.parse(source, headers: true)
deleted_values = table.delete('Value', 'Name')
deleted_values # => [["0", "1", "2"], ["foo", "bar", "baz"]]

Removes rows or columns for which the block returns a truthy value; returns self.

Removes rows when the access mode is :row or :col_or_row; calls the block with each CSV::Row object:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_row! # => #<CSV::Table mode:row row_count:4>
table.size # => 3
table.delete_if {|row| row['Name'].start_with?('b') }
table.size # => 1

Removes columns when the access mode is :col; calls the block with each column as a 2-element array containing the header and an Array of column fields:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_col! # => #<CSV::Table mode:col row_count:4>
table.headers.size # => 2
table.delete_if {|column_data| column_data[1].include?('2') }
table.headers.size # => 1

Returns a new Enumerator if no block is given:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.delete_if # => #<Enumerator: #<CSV::Table mode:col_or_row row_count:4>:delete_if>

Extracts the nested value specified by the sequence of index or header objects by calling dig at each step, returning nil if any intermediate step is nil.

Calls the block with each row or column; returns self.

When the access mode is :row or :col_or_row, calls the block with each CSV::Row object:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.by_row! # => #<CSV::Table mode:row row_count:4>
table.each {|row| p row }

Output:

#<CSV::Row "Name":"foo" "Value":"0">
#<CSV::Row "Name":"bar" "Value":"1">
#<CSV::Row "Name":"baz" "Value":"2">

When the access mode is :col, calls the block with each column as a 2-element array containing the header and an Array of column fields:

table.by_col! # => #<CSV::Table mode:col row_count:4>
table.each {|column_data| p column_data }

Output:

["Name", ["foo", "bar", "baz"]]
["Value", ["0", "1", "2"]]

Returns a new Enumerator if no block is given:

table.each # => #<Enumerator: #<CSV::Table mode:col row_count:4>:each>

Returns a new Array containing the String headers for the table.

If the table is not empty, returns the headers from the first row:

rows = [
  CSV::Row.new(['Foo', 'Bar'], []),
  CSV::Row.new(['FOO', 'BAR'], []),
  CSV::Row.new(['foo', 'bar'], []),
]
table  = CSV::Table.new(rows)
table.headers # => ["Foo", "Bar"]
table.delete(0)
table.headers # => ["FOO", "BAR"]
table.delete(0)
table.headers # => ["foo", "bar"]

If the table is empty, returns a copy of the headers in the table itself:

table.delete(0)
table.headers # => ["Foo", "Bar"]

Returns a US-ASCII-encoded String showing table:

• Class: CSV::Table.

• Access mode: :row, :col, or :col_or_row.

• Size: Row count, including the header row.

Example:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.inspect # => "#<CSV::Table mode:col_or_row row_count:4>\nName,Value\nfoo,0\nbar,1\nbaz,2\n"

A shortcut for appending multiple rows. Equivalent to:

rows.each {|row| self << row }

Each argument may be either a CSV::Row object or an Array:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
rows = [
  CSV::Row.new(table.headers, ['bat', 3]),
  ['bam', 4]
]
table.push(*rows)
table[3..4] # => [#<CSV::Row "Name":"bat" "Value":3>, #<CSV::Row "Name":"bam" "Value":4>]

Returns the table as an Array of Arrays; the headers are in the first row:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.to_a # => [["Name", "Value"], ["foo", "0"], ["bar", "1"], ["baz", "2"]]

Returns the table as CSV string. See Options for Generating.

Defaults option write_headers to true:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.to_csv # => "Name,Value\nfoo,0\nbar,1\nbaz,2\n"

Omits the headers if option write_headers is given as false (see {Option write_headers}):

table.to_csv(write_headers: false) # => "foo,0\nbar,1\nbaz,2\n"

Limit rows if option limit is given like 2:

table.to_csv(limit: 2) # => "Name,Value\nfoo,0\nbar,1\n"

If the access mode is :row or :col_or_row, and each argument is either an Integer or a Range, returns rows. Otherwise, returns columns data.

In either case, the returned values are in the order specified by the arguments. Arguments may be repeated.

Returns rows as an Array of CSV::Row objects.

No argument:

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.values_at # => []

One index:

values = table.values_at(0)
values # => [#<CSV::Row "Name":"foo" "Value":"0">]

Two indexes:

values = table.values_at(2, 0)
values # => [#<CSV::Row "Name":"baz" "Value":"2">, #<CSV::Row "Name":"foo" "Value":"0">]

One Range:

values = table.values_at(1..2)
values # => [#<CSV::Row "Name":"bar" "Value":"1">, #<CSV::Row "Name":"baz" "Value":"2">]

Ranges and indexes:

values = table.values_at(0..1, 1..2, 0, 2)
pp values

Output:

[#<CSV::Row "Name":"foo" "Value":"0">,
 #<CSV::Row "Name":"bar" "Value":"1">,
 #<CSV::Row "Name":"bar" "Value":"1">,
 #<CSV::Row "Name":"baz" "Value":"2">,
 #<CSV::Row "Name":"foo" "Value":"0">,
 #<CSV::Row "Name":"baz" "Value":"2">]

Returns columns data as row Arrays, each consisting of the specified columns data for that row:

values = table.values_at('Name')
values # => [["foo"], ["bar"], ["baz"]]
values = table.values_at('Value', 'Name')
values # => [["0", "foo"], ["1", "bar"], ["2", "baz"]]