Writing to files is essential in any programming language, including Python. Often we find ourselves in situations where we would need to write a list into a file. There are multiple approaches to writing a list to file in Python.<\/p>\n\n\n\n
Writing a list to file in Python consists of 5 steps regardless of the approach we take:<\/strong><\/p>\n\n\n\n Also, as already said, we can choose over multiple approaches:<\/p>\n\n\n\n First, let\u2019s see how to use the write method.<\/p>\n\n\n\n The Let\u2019s see the following example:<\/p>\n\n\n\n Our file is saved in the same directory as our script, and its output is:<\/p>\n\n\n\n Although this works, there is a better way to write a list to a file. In the example above, if the error appears, the file remains open, and that\u2019s not entirely safe behavior.<\/p>\n\n\n\n There are two other approaches to the problem mentioned above:<\/p>\n\n\n\n Using try-catch block, our above example would look like this:<\/p>\n\n\n\n This assures that we will successfully close the file even if the error appears. Even though this approach is better than the first one, Python supports closing files without explicitly calling the This approach implies using \u201cwith statement\u201d. \u201cWith statement\u201d is the practice of opening files in Python. We can use Python syntax to open a file, and Python will close it safely without the need for our implementation.<\/strong><\/p>\n\n\n\n Let\u2019s look at how to use \u201cwith statement\u201d when writing a list to a file in Python.<\/p>\n\n\n\n This is the best way to use Python to write a list to a file.<\/p>\n\n\n\n The But if we see our output, it looks like this:<\/p>\n\n\n\n This can be easily changed using the .join method, as seen in the following example:<\/p>\n\n\n\n Finally, we get our output formatted:<\/p>\n\n\n\n The The Usage of Our output looks somewhat different from other methods:<\/p>\n\n\n\n Our list was written to file in the same format we gave it to the Last but not least, we can use the The Here, we\u2019ll focus on the You can see little change from previous examples. We use Why is that? This method loaded our books list from the above example into the books variable.<\/p>\n\n\n\nwrite<\/code> method<\/strong><\/li>writelines<\/code> method<\/strong><\/li>json<\/code> module<\/strong><\/li>pickle<\/code> module<\/strong><\/li><\/ul>\n\n\n\nWrite a list to the file using the
write<\/code> method<\/h2>\n\n\n\nwrite<\/code> and writelines<\/code> methods belong to the TextIOWrapper<\/code> class. This class is initialized when the open()<\/code> function is called. TextIOWrapper<\/code> <\/strong>class is used for reading and writing files in Python.<\/p>\n\n\n\nbooks = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"] \nfile = open(\"file.txt\", \"w\")\nfor book in books:\n file.write(book + \"\\n\")\nfile.close()<\/pre>\n\n\n\n
$ cat file.txt\nRomeo and Juliet\nMacbeth\nHamlet<\/pre>\n\n\n\n
try:\n file = open(\"file.txt\", \"w\")\n\n books = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]\n for book in books:\n file.write(book + \"\\n\")\nfinally:\n file.close()<\/pre>\n\n\n\n
close()<\/code> method.<\/p>\n\n\n\nwith open('file.txt', \"w\") as file:\n books = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]\n for book in books:\n file.write(book + \"\\n\")<\/pre>\n\n\n\nWARNING<\/strong> - try-catch and \u201cwith statements\u201d are not equivalent. Using with statement is a better and safer approach.<\/pre>\n\n\n\n
Write a list to the file using the
writelines<\/code> method<\/h2>\n\n\n\nwritelines<\/code> method belongs to the already mentioned TextIOWrapper<\/code> class. The writelines<\/code> method, unlike the write<\/code> method, receives a whole list.<\/strong> The given list is written to a file without formatting and in a single line. That can, of course, be manipulated and changed.<\/p>\n\n\n\nwith open('file.txt', \"w\") as file:\n books = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]\n file.writelines(books)<\/pre>\n\n\n\n$ cat file.txt\nRomeo and JulietMacbethHamlet<\/pre>\n\n\n\n
with open('file.txt', \"w\") as file:\n books = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]\n file.writelines('\\n'.join(books))<\/pre>\n\n\n\n$ cat file.txt\nRomeo and Juliet\nMacbeth\nHamlet<\/pre>\n\n\n\n
Write a list to the file using the
json<\/code> module<\/h2>\n\n\n\njson<\/code> module is a very known module in the Python community. It helps us use JSON data format (similar to the dictionary in Python). But it also has support for writing to files. So how can we make use of that?<\/p>\n\n\n\njson<\/code> module has a <\/strong>dump<\/code> method that serializes the objects to files.<\/strong><\/p>\n\n\n\njson.dump<\/code> method can be seen in the following example:<\/p>\n\n\n\nimport json\n\nwith open('file.txt', 'w') as file:\n books = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]\n json.dump(books, file)<\/pre>\n\n\n\n$ cat file.txt\n[\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]<\/pre>\n\n\n\n
dump<\/code> method.<\/p>\n\n\n\npickle<\/code> module to write a list to a file in Python.<\/p>\n\n\n\nWrite a list to the file using the
pickle<\/code> module<\/h2>\n\n\n\npickle<\/code> module is a standard python module used for the serialization of objects.<\/strong> Also, this module has support for file reading and writing.<\/p>\n\n\n\ndump()<\/code> method. However, you can find other methods in the pickle module<\/a>.<\/p>\n\n\n\nimport pickle\n\nwith open('file.txt', 'wb') as file:\n books = [\"Romeo and Juliet\", \"Macbeth\", \"Hamlet\"]\n pickle.dump(books, file)<\/pre>\n\n\n\n\u2018wb\u2019<\/code> in the open function, which means we are writing binary data into a file.<\/p>\n\n\n\n
Dump works with binary data, and only like that data can be written to a file. Even though this data is not humanly readable, we can use it when we need to read the list from a file.<\/strong> Pickle added support for reading binary files and loading them into the list:<\/p>\n\n\n\nwith open('file.txt', 'rb') as file:\n books = pickle.load(file)<\/pre>\n\n\n\nConclusion<\/h2>\n\n\n\n