# `csv` --- CSV File Reading and Writing

Kode sumber: Lib/csv.py

Format CSV (Comma Separated Values) adalah format impor dan ekspor data yang paling umum digunakan untuk data spreadsheet dan database. Format CSV telah digunakan selama bertahun-tahun sebelum adanya upaya untuk mendeskripsikan format yang distandardisasi pada RFC 4180. Kurangnya standar yang terdefinisi dengan baik berarti banyak perbedaan tipis pada data yang dihasilkan dan digunakan dengan penggunaan yang berbeda. Perbedaan tersebut membuat tidak mudah untuk memproses file CSV dari beberapa sumber. Namun, meskipun karakter pembatas dan kutipan berbeda-beda, keseluruhan formatnya cukup mirip sehingga memungkinkan untuk menulis sebuah modul yang secara efisien dapat memanipulasi data tersebut.

Modul `csv` mengimplementasikan kelas-kelas untuk membaca dan menulis data tabular dengan format CSV. Hal ini memungkinkan pemrogram untuk mengatakan, "tulis data ini dalam format yang disukai oleh Excel," atau "baca data dari file ini yang dihasilkan oleh Excel," tanpa mengetahui detail persis dari format CSV yang digunakan oleh Excel. Pemrogram juga bisa mendeskripsikan format CSV yang dapat dipahami oleh aplikasi lain atau menentukan format CSV nya sendiri dengan tujuan tertentu.

Modul milik `csv`, `reader` dan `writer` objek membaca dan menulis urutan-urutan. Pemrogram juga bisa membaca dan menulis data dalam bentuk dictionary dengan menggunakan kelas `DictReader` dan `DictWriter`.

Lihat juga

PEP 305 - API File CSV

  Python Enhancement Proposal yang mengusulkan penambahan ini ke Python.

## Modul-Modul

Modul `csv` memiliki fungsi-fungsi sebagai berikut:

csv.reader(csvfile, /, dialect='excel', **fmtparams)

  Return a reader object that will process lines from the given csvfile. A csvfile must be an iterable of strings, each in the reader's defined csv format. A csvfile is most commonly a file-like object or list. If csvfile is a file object, it should be opened with `newline=''`. [1] An optional dialect parameter can be given which is used to define a set of parameters specific to a particular CSV dialect. It may be an instance of a subclass of the `Dialect` class or one of the strings returned by the `list_dialects()` function. The other optional fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect. For full details about the dialect and formatting parameters, see section Dialek dan Parameter Pemformatan.

  Each row read from the csv file is returned as a list of strings. No automatic data type conversion is performed unless the `QUOTE_NONNUMERIC` format option is specified (in which case unquoted fields are transformed into floats).

  Contoh penggunaan singkat:

      >>> import csv
      >>> with open('eggs.csv', newline='') as csvfile:
      ...     spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
      ...     for row in spamreader:
      ...         print(', '.join(row))
      Spam, Spam, Spam, Spam, Spam, Baked Beans
      Spam, Lovely Spam, Wonderful Spam

csv.writer(csvfile, /, dialect='excel', **fmtparams)

  Return a writer object responsible for converting the user's data into delimited strings on the given file-like object. csvfile can be any object with a `write()` method. If csvfile is a file object, it should be opened with `newline=''` [1]. An optional dialect parameter can be given which is used to define a set of parameters specific to a particular CSV dialect. It may be an instance of a subclass of the `Dialect` class or one of the strings returned by the `list_dialects()` function. The other optional fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect. For full details about dialects and formatting parameters, see the Dialek dan Parameter Pemformatan section. To make it as easy as possible to interface with modules which implement the DB API, the value `None` is written as the empty string. While this isn't a reversible transformation, it makes it easier to dump SQL NULL data values to CSV files without preprocessing the data returned from a `cursor.fetch*` call. All other non-string data are stringified with `str()` before being written.

  Contoh penggunaan singkat:

      import csv
      with open('eggs.csv', 'w', newline='') as csvfile:
          spamwriter = csv.writer(csvfile, delimiter=' ',
                                  quotechar='|', quoting=csv.QUOTE_MINIMAL)
          spamwriter.writerow(['Spam'] * 5 + ['Baked Beans'])
          spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])

csv.register_dialect(name, /, dialect='excel', **fmtparams)

  Associate dialect with name. name must be a string. The dialect can be specified either by passing a sub-class of `Dialect`, or by fmtparams keyword arguments, or both, with keyword arguments overriding parameters of the dialect. For full details about dialects and formatting parameters, see section Dialek dan Parameter Pemformatan.

csv.unregister_dialect(name)

  Delete the dialect associated with name from the dialect registry. An `Error` is raised if name is not a registered dialect name.

csv.get_dialect(name)

  Return the dialect associated with name. An `Error` is raised if name is not a registered dialect name. This function returns an immutable `Dialect`.

csv.list_dialects()

  Mengembalikan nama dari semua dialek yang terdaftar.

csv.field_size_limit()
csv.field_size_limit(new_limit)

  Mengembalikan nilai maksimum ukuran field yang diperbolekan saat ini oleh parser. Jika new_limit diberikan, hal tersebut menjadi limit baru.

Modul `csv` berisi kelas-kelas dibawah ini:

class csv.DictReader(f, fieldnames=None, restkey=None, restval=None, dialect='excel', *args, **kwds)

  Create an object that operates like a regular reader but maps the information in each row to a `dict` whose keys are given by the optional fieldnames parameter.

  The fieldnames parameter is a sequence. If fieldnames is omitted, the values in the first row of file f will be used as the fieldnames and will be omitted from the results. If fieldnames is provided, they will be used and the first row will be included in the results. Regardless of how the fieldnames are determined, the dictionary preserves their original ordering.

  If a row has more fields than fieldnames, the remaining data is put in a list and stored with the fieldname specified by restkey (which defaults to `None`). If a non-blank row has fewer fields than fieldnames, the missing values are filled-in with the value of restval (which defaults to `None`).

  All other optional or keyword arguments are passed to the underlying `reader` instance.

  If the argument passed to fieldnames is an iterator, it will be coerced to a `list`.

  Berubah pada versi 3.6: Baris-baris yang dikembalikan sekarang memiliki tipe `OrderedDict`.

  Berubah pada versi 3.8: Baris-baris yang dikembalikan sekarang memiliki tipe `dict`.

  Contoh penggunaan singkat:

      >>> import csv
      >>> with open('names.csv', newline='') as csvfile:
      ...     reader = csv.DictReader(csvfile)
      ...     for row in reader:
      ...         print(row['first_name'], row['last_name'])
      ...
      Eric Idle
      John Cleese

      >>> print(row)
      {'first_name': 'John', 'last_name': 'Cleese'}

class csv.DictWriter(f, fieldnames, restval='', extrasaction='raise', dialect='excel', *args, **kwds)

  Create an object which operates like a regular writer but maps dictionaries onto output rows. The fieldnames parameter is a `sequence` of keys that identify the order in which values in the dictionary passed to the `writerow()` method are written to file f. The optional restval parameter specifies the value to be written if the dictionary is missing a key in fieldnames. If the dictionary passed to the `writerow()` method contains a key not found in fieldnames, the optional extrasaction parameter indicates what action to take. If it is set to `'raise'`, the default value, a `ValueError` is raised. If it is set to `'ignore'`, extra values in the dictionary are ignored. Any other optional or keyword arguments are passed to the underlying `writer` instance.

  Note that unlike the `DictReader` class, the fieldnames parameter of the `DictWriter` class is not optional.

  If the argument passed to fieldnames is an iterator, it will be coerced to a `list`.

  Contoh penggunaan singkat:

      import csv

      with open('names.csv', 'w', newline='') as csvfile:
          fieldnames = ['first_name', 'last_name']
          writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

          writer.writeheader()
          writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})
          writer.writerow({'first_name': 'Lovely', 'last_name': 'Spam'})
          writer.writerow({'first_name': 'Wonderful', 'last_name': 'Spam'})

class csv.Dialect

  The `Dialect` class is a container class whose attributes contain information for how to handle doublequotes, whitespace, delimiters, etc. Due to the lack of a strict CSV specification, different applications produce subtly different CSV data. `Dialect` instances define how `reader` and `writer` instances behave.

  All available `Dialect` names are returned by `list_dialects()`, and they can be registered with specific `reader` and `writer` classes through their initializer (`__init__`) functions like this:

      import csv

      with open('students.csv', 'w', newline='') as csvfile:
          writer = csv.writer(csvfile, dialect='unix')

class csv.excel

  The `excel` class defines the usual properties of an Excel-generated CSV file. It is registered with the dialect name `'excel'`.

class csv.excel_tab

  The `excel_tab` class defines the usual properties of an Excel-generated TAB-delimited file. It is registered with the dialect name `'excel-tab'`.

class csv.unix_dialect

  The `unix_dialect` class defines the usual properties of a CSV file generated on UNIX systems, i.e. using `'\n'` as line terminator and quoting all fields. It is registered with the dialect name `'unix'`.

  Added in version 3.2.

class csv.Sniffer

  Kelas `Sniffer` digunakan untuk menyimpulkan format sebuah file CSV.

  Kelas `Sniffer` menyediakan dua metode:

  sniff(sample, delimiters=None)

    Analyze the given sample and return a `Dialect` subclass reflecting the parameters found. If the optional delimiters parameter is given, it is interpreted as a string containing possible valid delimiter characters.

  has_header(sample)

    Analyze the sample text (presumed to be in CSV format) and return `True` if the first row appears to be a series of column headers. Inspecting each column, one of two key criteria will be considered to estimate if the sample contains a header:

    - the second through n-th rows contain numeric values

    - the second through n-th rows contain strings where at least one value's length differs from that of the putative header of that column.

    Twenty-one rows after the header are sampled; if more than half of the columns + rows meet the criteria, `True` is returned.

  Catatan

  This method is a rough heuristic and may produce both false positives and negatives.

Sebuah contoh untuk penggunaan `Sniffer`:

    with open('example.csv', newline='') as csvfile:
        dialect = csv.Sniffer().sniff(csvfile.read(1024))
        csvfile.seek(0)
        reader = csv.reader(csvfile, dialect)
        # ... process CSV file contents here ...

The `csv` module defines the following constants:

csv.QUOTE_ALL

  Menginstruksikan objek `writer` untuk mengutip semua fields.

csv.QUOTE_MINIMAL

  Instructs `writer` objects to only quote those fields which contain special characters such as delimiter, quotechar, `'\r'`, `'\n'` or any of the characters in lineterminator.

csv.QUOTE_NONNUMERIC

  Menginstuksikan objek `writer` untuk mengutip semua fields yang tidak memiliki angka.

  Instructs `reader` objects to convert all non-quoted fields to type `float`.

  Catatan

  Some numeric types, such as `bool`, `Fraction`, or `IntEnum`, have a string representation that cannot be converted to `float`. They cannot be read in the `QUOTE_NONNUMERIC` and `QUOTE_STRINGS` modes.

csv.QUOTE_NONE

  Instructs `writer` objects to never quote fields. When the current delimiter, quotechar, escapechar, `'\r'`, `'\n'` or any of the characters in lineterminator occurs in output data it is preceded by the current escapechar character. If escapechar is not set, the writer will raise `Error` if any characters that require escaping are encountered. Set quotechar to `None` to prevent its escaping.

  Instructs `reader` objects to perform no special processing of quote characters.

csv.QUOTE_NOTNULL

  Instructs `writer` objects to quote all fields which are not `None`. This is similar to `QUOTE_ALL`, except that if a field value is `None` an empty (unquoted) string is written.

  Instructs `reader` objects to interpret an empty (unquoted) field as `None` and to otherwise behave as `QUOTE_ALL`.

  Added in version 3.12.

csv.QUOTE_STRINGS

  Instructs `writer` objects to always place quotes around fields which are strings. This is similar to `QUOTE_NONNUMERIC`, except that if a field value is `None` an empty (unquoted) string is written.

  Instructs `reader` objects to interpret an empty (unquoted) string as `None` and to otherwise behave as `QUOTE_NONNUMERIC`.

  Added in version 3.12.

Modul `csv` berisi exception dibawah ini:

exception csv.Error

  Raised by any of the functions when an error is detected.

## Dialek dan Parameter Pemformatan

To make it easier to specify the format of input and output records, specific formatting parameters are grouped together into dialects. A dialect is a subclass of the `Dialect` class containing various attributes describing the format of the CSV file. When creating `reader` or `writer` objects, the programmer can specify a string or a subclass of the `Dialect` class as the dialect parameter. In addition to, or instead of, the dialect parameter, the programmer can also specify individual formatting parameters, which have the same names as the attributes defined below for the `Dialect` class.

Dialek mendukung atribut dibawah ini:

Dialect.delimiter

  Sebuah karakter yang digunakan sebagai pemisah fields. Dengan nilai bawaan `','`.

Dialect.doublequote

  Controls how instances of quotechar appearing inside a field should themselves be quoted. When `True`, the character is doubled. When `False`, the escapechar is used as a prefix to the quotechar. It defaults to `True`.

  On output, if doublequote is `False` and no escapechar is set, `Error` is raised if a quotechar is found in a field.

Dialect.escapechar

  A one-character string used by the writer to escape characters that require escaping:

  > - the delimiter, the quotechar, `'\r'`, `'\n'` and any of the characters in lineterminator are escaped if quoting is set to `QUOTE_NONE`;

  > - the quotechar is escaped if doublequote is `False`;

  > - the escapechar itself.

  On reading, the escapechar removes any special meaning from the following character. It defaults to `None`, which disables escaping.

  Berubah pada versi 3.11: An empty escapechar is not allowed.

Dialect.lineterminator

  The string used to terminate lines produced by the `writer`. It defaults to `'\r\n'`.

  Catatan

  The `reader` is hard-coded to recognise either `'\r'` or `'\n'` as end-of-line, and ignores lineterminator. This behavior may change in the future.

Dialect.quotechar

  A one-character string used to quote fields containing special characters, such as the delimiter or the quotechar, or which contain new-line characters (`'\r'`, `'\n'` or any of the characters in lineterminator). It defaults to `'"'`. Can be set to `None` to prevent escaping `'"'` if quoting is set to `QUOTE_NONE`.

  Berubah pada versi 3.11: An empty quotechar is not allowed.

Dialect.quoting

  Controls when quotes should be generated by the writer and recognised by the reader. It can take on any of the QUOTE_* constants and defaults to `QUOTE_MINIMAL` if quotechar is not `None`, and `QUOTE_NONE` otherwise.

Dialect.skipinitialspace

  When `True`, spaces immediately following the delimiter are ignored. The default is `False`. When combining `delimiter=' '` with `skipinitialspace=True`, unquoted empty fields are not allowed.

Dialect.strict

  When `True`, raise exception `Error` on bad CSV input. The default is `False`.

## Reader Objects

Reader objects (`DictReader` instances and objects returned by the `reader()` function) have the following public methods:

csvreader.__next__()

  Return the next row of the reader's iterable object as a list (if the object was returned from `reader()`) or a dict (if it is a `DictReader` instance), parsed according to the current `Dialect`. Usually you should call this as `next(reader)`.

Reader objects have the following public attributes:

csvreader.dialect

  A read-only description of the dialect in use by the parser.

csvreader.line_num

  The number of lines read from the source iterator. This is not the same as the number of records returned, as records can span multiple lines.

Objek DictReader memiliki atribut publik sebagai berikut:

DictReader.fieldnames

  If not passed as a parameter when creating the object, this attribute is initialized upon first access or when the first record is read from the file.

## Writer Objects

`writer` objects (`DictWriter` instances and objects returned by the `writer()` function) have the following public methods. A row must be an iterable of strings or numbers for `writer` objects and a dictionary mapping fieldnames to strings or numbers (by passing them through `str()` first) for `DictWriter` objects. Note that complex numbers are written out surrounded by parens. This may cause some problems for other programs which read CSV files (assuming they support complex numbers at all).

csvwriter.writerow(row, /)

  Write the row parameter to the writer's file object, formatted according to the current `Dialect`. Return the return value of the call to the write method of the underlying file object.

  Berubah pada versi 3.5: Added support of arbitrary iterables.

csvwriter.writerows(rows, /)

  Write all elements in rows (an iterable of row objects as described above) to the writer's file object, formatted according to the current dialect.

Writer objects have the following public attribute:

csvwriter.dialect

  A read-only description of the dialect in use by the writer.

Objek DictWriter memiliki metode publik sebagai berikut:

DictWriter.writeheader()

  Write a row with the field names (as specified in the constructor) to the writer's file object, formatted according to the current dialect. Return the return value of the `csvwriter.writerow()` call used internally.

  Added in version 3.2.

  Berubah pada versi 3.8: `writeheader()` now also returns the value returned by the `csvwriter.writerow()` method it uses internally.

## Contoh-contoh

Contoh paling sederhana dari membaca sebuah file CSV:

    import csv
    with open('some.csv', newline='') as f:
        reader = csv.reader(f)
        for row in reader:
            print(row)

Membaca file dengan format lain:

    import csv
    with open('passwd', newline='') as f:
        reader = csv.reader(f, delimiter=':', quoting=csv.QUOTE_NONE)
        for row in reader:
            print(row)

Contoh paling sederhana dari menulis ke sebuah file CSV:

    import csv
    with open('some.csv', 'w', newline='') as f:
        writer = csv.writer(f)
        writer.writerows(someiterable)

Since `open()` is used to open a CSV file for reading, the file will by default be decoded into unicode using the system default encoding (see `locale.getencoding()`). To decode a file using a different encoding, use the `encoding` argument of open:

    import csv
    with open('some.csv', newline='', encoding='utf-8') as f:
        reader = csv.reader(f)
        for row in reader:
            print(row)

Hal yang sama berlaku ketika menulis sesuatu yang berbeda dengan default encoding dari sistem: tentukan argumen encoding ketika membuka file output.

Mendaftarkan dialek baru:

    import csv
    csv.register_dialect('unixpwd', delimiter=':', quoting=csv.QUOTE_NONE)
    with open('passwd', newline='') as f:
        reader = csv.reader(f, 'unixpwd')

A slightly more advanced use of the reader --- catching and reporting errors:

    import csv, sys
    filename = 'some.csv'
    with open(filename, newline='') as f:
        reader = csv.reader(f)
        try:
            for row in reader:
                print(row)
        except csv.Error as e:
            sys.exit(f'file {filename}, line {reader.line_num}: {e}')

And while the module doesn't directly support parsing strings, it can easily be done:

    import csv
    for row in csv.reader(['one,two,three']):
        print(row)

Catatan kaki

[1] (1,2)

If `newline=''` is not specified, newlines embedded inside quoted fields will not be interpreted correctly, and on platforms that use `\r\n` line endings on write an extra `\r` will be added. It should always be safe to specify `newline=''`, since the csv module does its own (universal) newline handling.