Python create list file

6 Methods to write a list to text File in Python

In this post, We are going to learn 6 Methods to write a list to text File in Python, we have a built-in method for writing a file. While programming we have to write a lot of data to be stored in the computer except the data structure list object in memory to perform a further operation or store it for later use.

How to create a file in Python

Using open() method

it takes two arguments, The first is the file name, and the second represents the mode(permission) of the file. To create a file in python, we use the following syntax.

Syntax

file = open("File_Name", "Access_Mode")

The name of the file is ‘devenum.txt’, and ‘w’ represents that we want to create a new file if it does not exist, Also that has permission to write.

Steps to create a text file

• Open the file using the open() method in write mode using ‘w’. The point to note here is that the ‘w’ specifier creates a new file, if the file does not exist else overwrite the existing file.
• Write to file using write() method
• Close a file using a close() method.

1.Program example: Create a file object and write data

The above code of writing file can be simplified with lesser code using with a statement

with open('devenum.txt', 'w') as file_list: file_list.write('my firt file\n')

To write a Python list into a file in we have these methods

1. Write() method to Write a list line by line

To write a list into a file line by line we will use the write () method. We are creating a file in write mode and loop over the element of the list one by one as well to write them in the file. In this line my_list_file.write(‘%s\n’ % element) we are terminating each line by a special character that is EOF(end of file) or newline (\n) or line break.

#list of programming langauges lang_lst = ['C#','Pyhthon','Go','Data','C#','16','17','35','68'] with open('devenum.txt', 'w') as my_list_file: #looping over the each ist element for element in lang_lst: #writing to file line by line my_list_file.write('%s\n' % element)

Created file “devenum.txt” content is shown in the output

C# Pyhthon Go Data C# 16 17 35 68

2. Using join() and write() method to write list to file

In this example, we join all the lists using the join() method and then writing all the list elements in one go. In this way, we don’t need to loop over each item on the list.

#list of programming langauges lang_lst = ['C#','Python','Go','Data','C#','16','17','35','68'] with open('devenum.txt', 'w') as my_list_file: file_content = "\n".join(lang_lst) my_list_file.write(file_content)

C# Python Go Data C# 16 17 35 68

3. Write entire list using writelines() method

the writelines() is a multiline method() that we often use to write an entire list into a file in one go. Let us understand with an example of how we can do this.

writelines() using looping over each element

We are looping over the elements of list in writelines() and writing line by line.

#defining a list lang_lst = ['C#','Python','Go','Data','C#','16','17','35','68'] with open('devenum.txt', 'w') as my_list_file: my_list_file.writelines("%s\n" % lang for lang in lang_lst)

The content of created file “devenum.txt” is shown in the output

C# Python Go Data C# 16 17 35 68

writeline() to write a list object in file

We can pass the list directly using the writeline() method.

#list of programming langauges lang_lst = ['C#','Python','Go','Data','C#','16','17','35','68'] with open('devenum.txt', 'w') as my_list_file: my_list_file.writelines("%s\n" % lang_lst)

Created file “devenum.txt” content is shown in the output

['C#', 'Python', 'Go', 'Data', 'C#', '16', '17', '35', '68']

4. Write a list into file using JSON

Another way to write the list file in JSON format in the text file using the JSON Module. We dump the list using the JSON module DUMP() method. The process is the same as we have seen in the above example. More we can understand with an example.

import json #list of programming langauges lang_lst = ['C#','Pyhthon','Go','Data','C#','16','17','35','68'] with open('devenum.txt', 'w') as my_list_file: json.dump(lang_lst, my_list_file)

The output will be as shown below in devenum.txt file.

["C#", "Pyhthon", "Go", "Data", "C#", "16", "17", "35", "68"]

5. unpack operator with print() method

The unpack operator(*) unpack an iterable(list,dictionary,tuple).We can use it with print() method to convert list to a file.

import pickle #list of programming langauges lang_lst = ['C#','Pyhthon','Go','Data','C#','16','17','35','68'] with open('devenum.txt', 'w') as my_list_file: print(*lang_lst,sep="\n",file= my_list_file)

6.NumPy savetxt() method to write a list to text file

we can use Numpy.savetxt() method converts an array or list to a text file. The frm argument use to specifying the format of the file and delimiter parameter for a set delimiter.

We don’t need to open files using Numpy.savetxt() method.

import numpy as np #list of programming langauges lang_lst = ['C#','Pyhthon','Go','Data','C#','16','17','35','68'] np.savetxt('devenum.txt',lang_lst,delimiter="\n", fmt="%s")

Conclusion:

We have explored 4 Methods to write a list to text File that includes single-line multi-line and JSON.

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Python Program to Write List to File

The List in Python is a built-in data structure that stores heterogeneous or homogeneous data in a sequential form. Elements in a list may be unique or duplicates and are identified by a unique position called an index. Python writes list to file and saves the data contained in the list to a text file.

How to Write List to File in Python

The write() or writelines() method helps Python write lists to files. A list in Python can be written in a file in various ways. The basic steps include:

• Open a text file in write mode
• Write current items from the list into the text file
• Close the file after completing the write operation

Method 1: Using write()

The list is iterated using a loop, and during every iteration, the write() method writes an item from the list to the file along with a newline character.

1. Open a .txt file function in w mode (here w signifies write). The open() function shows the file path.
2. Next, create a list of items. Using a for loop to iterate through all the items in the list.
3. The write() function adds the list of items to the text file.
4. Close the file using the close() function.

Method 2: Using writelines()

The writelines() takes a list as its argument and writes all the elements of the list to a file. In the text file, the list elements are appended one after another without any space or newline characters.

1. Open a .txt file function in w mode (here w signifies write). The open() function shows the file path.
2. Create a list of items.
3. The writelines() function takes the list of items as its parameter and writes them in the text file.
4. Close the file using the close() function.

Method 3: Using String Join Along with «with open» syntax

The with open syntax automatically closes the file after executing all statements inside it. Thus, the close() function does not need to be called explicitly.

1. Create a list of items.
2. Open a .txt file function in w mode (here w signifies write). The open() function shows the file path.
3. The write function in this block adds the list of items to the text file.

Which is the Best Method to Write a List to File in Python?

The simplest solution for Python to write the list to a file is to use a file.write() method that writes all the items from the list to a file. The open() method opens the file in w mode. The list is looped through and all the items are written one by one.

FAQs

1. What does access mode ‘w’ mean?

The w mode refers to writing. It creates a new file if a file with the specified name is absent, else overwrites the existing file.

2. How many arguments does the open() function take?

The open() function takes two arguments the filename along with its complete path, and the access mode.

3. How many arguments does the close() function take?

The close() function doesn’t take any argument.

4. Why is using the with open() method not safe?

In the case of with open() , if some exception occurs while opening the file, then the code exits without closing the file.

Similar Python Programs

Conclusion

• Creating, reading, opening, writing, and closing files using Python comes under File Handling.
• Python write list to file can be implemented using multiple ways.
• write() method inserts a string to a single line in a text file.
• writelines() is used for inserting multiple strings from a list of strings to the text file simultaneously.
• No close() statement is required as with open syntax automatically closes the file after executing all statements inside it.

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Writing a List to a File in Python — A Step-by-Step Guide

In Python, a list is a common data type for storing multiple values in the same place for easy access. These values could be numbers, strings, or objects.

Sometimes, it’s useful to write the contents of a list to an external file.

To write a Python list to a file:

1. Open a new file.
2. Separate the list of strings by a new line.
3. Add the result to a text file.

Here is an example code that shows how to do it:

names = ["Alice", "Bob", "Charlie"] with open("example.txt", mode="w") as file: file.write("\n".join(names))

As a result, you should see a text file with the names separated by a line break.

Obviously, this is only one approach. If you are not satisfied with it, see the other examples below.

Write List to File As-Is

You cannot directly write a list to a file. But you can convert the list to a string, and then write it.

names = ["Alice", "Bob", "Charlie"] with open("example.txt", mode="w") as file: file.write(str(names))

As a result, you see a text file called example.txt with the following contents:

Write List to File Comma-Separated without Brackets

To write a list into a text file with comma-separated values without brackets, use string.join() method.

names = ["Alice", "Bob", "Charlie"] with open("example.txt", mode="w") as file: file.write(", ".join(names))

As a result, you see a text file called example.txt with the following contents:

Write Python List to File Tab-Delimited

Sometimes you might want to write the list contents into an external file by using tabs as separators between the values.

To do this, you need to use the string.join() method to join the list elements by using a tab as a separator.

names = ["Alice", "Bob", "Charlie"] with open("example.txt", mode="w") as file: file.write("\t".join(names))

The result is a file called example.txt with the following contents tab-separated:

Conclusion

Today you learned how to write a list to a file in Python.

To recap, all you need to do is open a file, separate the strings, and write them into the file. All this happens by using the native methods in Python in a couple of lines of code.

Thanks for reading. I hope you enjoy it.

Further Reading

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