Dalam tutorial ini, kita akan belajar menulis file CSV dengan format berbeda dengan Python dengan bantuan contoh.
Kami akan secara eksklusif menggunakan csvmodul yang dibangun ke dalam Python untuk tugas ini. Tapi pertama-tama, kita harus mengimpor modul sebagai:
import csv
Kami telah membahas dasar-dasar cara menggunakan csvmodul untuk membaca dan menulis ke dalam file CSV. Jika Anda tidak tahu cara menggunakan csvmodul ini, lihat tutorial kami tentang CSV Python: Membaca dan Menulis file CSV
Penggunaan Dasar csv.writer ()
Mari kita lihat contoh dasar penggunaan csv.writer()untuk menyegarkan pengetahuan Anda yang sudah ada.
Contoh 1: Menulis ke file CSV dengan csv.writer ()
Misalkan kita ingin menulis file CSV dengan entri berikut:
SN, Nama, Kontribusi 1, Linus Torvalds, Linux Kernel 2, Tim Berners-Lee, World Wide Web 3, Guido van Rossum, Pemrograman Python
Begini cara kami melakukannya.
import csv with open('innovators.csv', 'w', newline='') as file: writer = csv.writer(file) writer.writerow(("SN", "Name", "Contribution")) writer.writerow((1, "Linus Torvalds", "Linux Kernel")) writer.writerow((2, "Tim Berners-Lee", "World Wide Web")) writer.writerow((3, "Guido van Rossum", "Python Programming"))
Ketika kami menjalankan program di atas, file innovators.csv dibuat di direktori kerja saat ini dengan entri yang diberikan.
Di sini, kami telah membuka file inovators.csv dalam mode penulisan menggunakan open()fungsi.
Untuk mempelajari lebih lanjut tentang membuka file dengan Python, kunjungi: Python File Input / Output
Selanjutnya csv.writer()fungsi tersebut digunakan untuk membuat sebuah writerobjek. The writer.writerow()Fungsi kemudian digunakan untuk menulis baris tunggal ke file CSV.
Contoh 2: Menulis Banyak Baris dengan writerows ()
Jika kita perlu menulis konten dari daftar 2 dimensi ke file CSV, berikut cara melakukannya.
import csv row_list = (("SN", "Name", "Contribution"), (1, "Linus Torvalds", "Linux Kernel"), (2, "Tim Berners-Lee", "World Wide Web"), (3, "Guido van Rossum", "Python Programming")) with open('protagonist.csv', 'w', newline='') as file: writer = csv.writer(file) writer.writerows(row_list)
Output dari program ini sama seperti pada Contoh 1 .
Di sini, daftar 2 dimensi kami diteruskan ke writer.writerows()fungsi untuk menulis konten daftar ke file CSV.
Sekarang mari kita lihat bagaimana kita dapat menulis file CSV dalam format yang berbeda. Kami kemudian akan belajar bagaimana menyesuaikan csv.writer()fungsi untuk menulisnya.
File CSV dengan Pembatas Kustom
Secara default, koma digunakan sebagai pembatas di file CSV. Namun, beberapa file CSV dapat menggunakan pembatas selain koma. Beberapa yang populer adalah |dan .
Misalkan kita ingin menggunakan |sebagai pembatas di file innovators.csv dari Contoh 1 . Untuk menulis file ini, kita dapat mengirimkan delimiterparameter tambahan ke csv.writer()fungsi tersebut.
Mari kita ambil contoh.
Contoh 3: Menulis File CSV dengan Pembatas Pipa
import csv data_list = (("SN", "Name", "Contribution"), (1, "Linus Torvalds", "Linux Kernel"), (2, "Tim Berners-Lee", "World Wide Web"), (3, "Guido van Rossum", "Python Programming")) with open('innovators.csv', 'w', newline='') as file: writer = csv.writer(file, delimiter='|') writer.writerows(data_list)
Keluaran
SN | Nama | Kontribusi 1 | Linus Torvalds | Kernel Linux 2 | Tim Berners-Lee | World Wide Web 3 | Guido van Rossum | Pemrograman Python
Seperti yang bisa kita lihat, parameter opsional delimiter = '|'membantu menentukan writerobjek yang harus dimiliki file CSV |sebagai pembatas.
File CSV dengan Kutipan
Beberapa file CSV memiliki tanda kutip di sekitar setiap atau beberapa entri.
Mari kita ambil quotes.csv sebagai contoh, dengan entri berikut:
"SN";"Name";"Quotes" 1;"Buddha";"What we think we become" 2;"Mark Twain";"Never regret anything that made you smile" 3;"Oscar Wilde";"Be yourself everyone else is already taken"
Using csv.writer() by default will not add these quotes to the entries.
In order to add them, we will have to use another optional parameter called quoting.
Let's take an example of how quoting can be used around the non-numeric values and ; as delimiters.
Example 4: Write CSV files with quotes
import csv row_list = ( ("SN", "Name", "Quotes"), (1, "Buddha", "What we think we become"), (2, "Mark Twain", "Never regret anything that made you smile"), (3, "Oscar Wilde", "Be yourself everyone else is already taken") ) with open('quotes.csv', 'w', newline='') as file: writer = csv.writer(file, quoting=csv.QUOTE_NONNUMERIC, delimiter=';') writer.writerows(row_list)
Output
"SN";"Name";"Quotes" 1;"Buddha";"What we think we become" 2;"Mark Twain";"Never regret anything that made you smile" 3;"Oscar Wilde";"Be yourself everyone else is already taken"
Here, the quotes.csv file is created in the working directory with the above entries.
As you can see, we have passed csv.QUOTE_NONNUMERIC to the quoting parameter. It is a constant defined by the csv module.
csv.QUOTE_NONNUMERIC specifies the writer object that quotes should be added around the non-numeric entries.
There are 3 other predefined constants you can pass to the quoting parameter:
csv.QUOTE_ALL- Specifies thewriterobject to write CSV file with quotes around all the entries.csv.QUOTE_MINIMAL- Specifies thewriterobject to only quote those fields which contain special characters (delimiter, quotechar or any characters in lineterminator)csv.QUOTE_NONE- Specifies thewriterobject that none of the entries should be quoted. It is the default value.
CSV files with custom quoting character
We can also write CSV files with custom quoting characters. For that, we will have to use an optional parameter called quotechar.
Let's take an example of writing quotes.csv file in Example 4, but with * as the quoting character.
Example 5: Writing CSV files with custom quoting character
import csv row_list = ( ("SN", "Name", "Quotes"), (1, "Buddha", "What we think we become"), (2, "Mark Twain", "Never regret anything that made you smile"), (3, "Oscar Wilde", "Be yourself everyone else is already taken") ) with open('quotes.csv', 'w', newline='') as file: writer = csv.writer(file, quoting=csv.QUOTE_NONNUMERIC, delimiter=';', quotechar='*') writer.writerows(row_list)
Output
*SN*;*Name*;*Quotes* 1;*Buddha*;*What we think we become* 2;*Mark Twain*;*Never regret anything that made you smile* 3;*Oscar Wilde*;*Be yourself everyone else is already taken*
Here, we can see that quotechar='*' parameter instructs the writer object to use * as quote for all non-numeric values.
Dialects in CSV module
Notice in Example 5 that we have passed multiple parameters (quoting, delimiter and quotechar) to the csv.writer() function.
This practice is acceptable when dealing with one or two files. But it will make the code more redundant and ugly once we start working with multiple CSV files with similar formats.
As a solution to this, the csv module offers dialect as an optional parameter.
Dialect helps in grouping together many specific formatting patterns like delimiter, skipinitialspace, quoting, escapechar into a single dialect name.
It can then be passed as a parameter to multiple writer or reader instances.
Example 6: Write CSV file using dialect
Suppose we want to write a CSV file (office.csv) with the following content:
"ID"|"Name"|"Email" "A878"|"Alfonso K. Hamby"|"[email protected]" "F854"|"Susanne Briard"|"[email protected]" "E833"|"Katja Mauer"|"[email protected]"
The CSV file has quotes around each entry and uses | as a delimiter.
Instead of passing two individual formatting patterns, let's look at how to use dialects to write this file.
import csv row_list = ( ("ID", "Name", "Email"), ("A878", "Alfonso K. Hamby", "[email protected]"), ("F854", "Susanne Briard", "[email protected]"), ("E833", "Katja Mauer", "[email protected]") ) csv.register_dialect('myDialect', delimiter='|', quoting=csv.QUOTE_ALL) with open('office.csv', 'w', newline='') as file: writer = csv.writer(file, dialect='myDialect') writer.writerows(row_list)
Output
"ID"|"Name"|"Email" "A878"|"Alfonso K. Hamby"|"[email protected]" "F854"|"Susanne Briard"|"[email protected]" "E833"|"Katja Mauer"|"[email protected]"
Here, office.csv is created in the working directory with the above contents.
From this example, we can see that the csv.register_dialect() function is used to define a custom dialect. Its syntax is:
csv.register_dialect(name(, dialect(, **fmtparams)))
The custom dialect requires a name in the form of a string. Other specifications can be done either by passing a sub-class of the Dialect class, or by individual formatting patterns as shown in the example.
While creating the writer object, we pass dialect='myDialect' to specify that the writer instance must use that particular dialect.
The advantage of using dialect is that it makes the program more modular. Notice that we can reuse myDialect to write other CSV files without having to re-specify the CSV format.
Write CSV files with csv.DictWriter()
The objects of csv.DictWriter() class can be used to write to a CSV file from a Python dictionary.
The minimal syntax of the csv.DictWriter() class is:
csv.DictWriter(file, fieldnames)
Here,
file- CSV file where we want to write tofieldnames- alistobject which should contain the column headers specifying the order in which data should be written in the CSV file
Example 7: Python csv.DictWriter()
import csv with open('players.csv', 'w', newline='') as file: fieldnames = ('player_name', 'fide_rating') writer = csv.DictWriter(file, fieldnames=fieldnames) writer.writeheader() writer.writerow(('player_name': 'Magnus Carlsen', 'fide_rating': 2870)) writer.writerow(('player_name': 'Fabiano Caruana', 'fide_rating': 2822)) writer.writerow(('player_name': 'Ding Liren', 'fide_rating': 2801))
Output
The program creates a players.csv file with the following entries:
player_name,fide_rating Magnus Carlsen,2870 Fabiano Caruana,2822 Ding Liren,2801
The full syntax of the csv.DictWriter() class is:
csv.DictWriter(f, fieldnames, restval='', extrasaction='raise', dialect='excel', *args, **kwds)
To learn more about it in detail, visit: Python csv.DictWriter() class
CSV files with lineterminator
A lineterminator is a string used to terminate lines produced by writer objects. The default value is . You can change its value by passing any string as a lineterminator parameter.
However, the reader object only recognizes or as lineterminator values. So using other characters as line terminators is highly discouraged.
doublequote & escapechar in CSV module
In order to separate delimiter characters in the entries, the csv module by default quotes the entries using quotation marks.
So, if you had an entry: He is a strong, healthy man, it will be written as: "He is a strong, healthy man".
Similarly, the csv module uses double quotes in order to escape the quote character present in the entries by default.
If you had an entry: Go to "programiz.com", it would be written as: "Go to ""programiz.com""".
Here, we can see that each " is followed by a " to escape the previous one.
doublequote
It handles how quotechar present in the entry themselves are quoted. When True, the quoting character is doubled and when False, the escapechar is used as a prefix to the quotechar. By default its value is True.
escapechar
escapechar parameter is a string to escape the delimiter if quoting is set to csv.QUOTE_NONE and quotechar if doublequote is False. Its default value is None.
Example 8: Using escapechar in csv writer
import csv row_list = ( ('Book', 'Quote'), ('Lord of the Rings', '"All we have to decide is what to do with the time that is given us."'), ('Harry Potter', '"It matters not what someone is born, but what they grow to be."') ) with open('book.csv', 'w', newline='') as file: writer = csv.writer(file, escapechar='/', quoting=csv.QUOTE_NONE) writer.writerows(row_list)
Output
Book,Quote Lord of the Rings,/"All we have to decide is what to do with the time that is given us./" Harry Potter,/"It matters not what someone is born/, but what they grow to be./"
Here, we can see that / is prefix to all the " and , because we specified quoting=csv.QUOTE_NONE.
If it wasn't defined, then, the output would be:
Book,Quote Lord of the Rings,"""All we have to decide is what to do with the time that is given us.""" Harry Potter,"""It matters not what someone is born, but what they grow to be."""
Since we allow quoting, the entries with special characters(" in this case) are double-quoted. The entries with delimiter are also enclosed within quote characters.(Starting and closing quote characters)
The remaining quote characters are to escape the actual " present as part of the string, so that they are not interpreted as quotechar.
Note: The csv module can also be used for other file extensions (like: .txt) as long as their contents are in proper structure.
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