Read First Line to See How Many Values Need to Be Read

In Python, there are a few ways you tin read a text file.

In this article, I volition go over the open() part, the read(), readline(), readlines(), close() methods, and the with keyword.

What is the open() function in Python?

If yous want to read a text file in Python, you lot kickoff have to open information technology.

This is the basic syntax for Python's open() function:

                open up("name of file you want opened", "optional fashion")              

File names and right paths

If the text file and your current file are in the same directory ("folder"), so you can but reference the file name in the open up() function.

                open("demo.txt")              

Here is an example of both files existence in the same directory:

If your text file is in a different directory, then you will need to reference the right path name for the text file.

In this example, the random-text file is inside a different binder then main.py:

In order to access that file in the main.py, you have to include the folder name with the name of the file.

                open("text-files/random-text.txt")              

If y'all don't have the correct path for the file, then y'all will go an mistake bulletin like this:

                open("random-text.txt")              

Information technology is really important to go on runway of which directory yous are in and then you can reference the correct path name.

Optional Mode parameter in open up()

In that location are different modes when you are working with files. The default mode is the read manner.

The alphabetic character r stands for read way.

                open("demo.txt", mode="r")              

You can also omit way= and simply write "r".

                open up("demo.txt", "r")              

There are other types of modes such as "w" for writing or "a" for appending.  I am non going to go into detail for the other modes because we are but going to focus on reading files.

For a complete listing of the other modes, please read through the documentation.

Boosted parameters for the open up() function in Python

The open() function tin can take in these optional parameters.

• buffering
• encoding
• errors
• newline
• closefd
• opener

To learn more about these optional parameters, delight read through the documentation.

What is the readable() method in Python?

If you desire to bank check if a file tin be read, then you can employ the readable() method. This will return a Truthful or False.

This example would render Truthful because nosotros are in the read mode:

                file = open("demo.txt") print(file.readable())              

If I changed this case, to "w" (write) mode, then the readable() method would return False:

                file = open("demo.txt", "due west") print(file.readable())              

What is the read() method in Python?

The read() method is going to read all of the content of the file as one string. This is a skillful method to apply if y'all don't have a lot of content in the text file.

In this case, I am using the read() method to impress out a list of names from the demo.txt file:

                file = open up("demo.txt") print(file.read())              

This method can have in an optional parameter called size. Instead of reading the whole file, only a portion of it will be read.

If we modify the earlier example, we tin print out only the kickoff give-and-take by adding the number iv as an argument for read().

                file = open("demo.txt") print(file.read(4))              

If the size argument is omitted, or if the number is negative, then the whole file will exist read.

What is the close() method in Python?

Once you are done reading a file, it is important that you close it. If y'all forget to close your file, then that tin cause bug.

This is an case of how to close the demo.txt file:

                file = open("demo.txt") print(file.read()) file.close()              

How to use the with keyword to close files in Python

One style to ensure that your file is airtight is to employ the with keyword. This is considered good practice, considering the file will close automatically instead of you having to manually close it.

Here is how to rewrite our example using the with keyword:

                with open("demo.txt") as file:     print(file.read())              

What is the readline() method in Python?

This method is going to read one line from the file and render that.

In this instance, nosotros take a text file with these two sentences:

                This is the starting time line This is the 2d line              

If nosotros utilize the readline() method, it volition only print the offset sentence of the file.

                with open("demo.txt") as file:     print(file.readline())              

This method besides takes in the optional size parameter. We can modify the example to add the number vii to but read and print out This is:

                with open up("demo.txt") as file:     print(file.readline(7))              

What is the readlines() method in Python?

This method volition read and return a list of all of the lines in the file.

In this case, we are going to impress out our grocery items as a list using the readlines() method.

                with open up("demo.txt") equally file:     print(file.readlines())              

How to use a for loop to read lines from a file in Python

An alternative to these different read methods would be to use a for loop.

In this example, we can print out all of the items in the demo.txt file past looping over the object.

                with open up("demo.txt") as file:     for item in file:         print(item)              

Conclusion

If y'all want to read a text file in Python, you lot first have to open it.

                open up("name of file y'all want opened", "optional style")                              

If the text file and your current file are in the same directory ("folder"), so you can simply reference the file proper name in the open() office.

If your text file is in a unlike directory, then you will need to reference the correct path name for the text file.

The open() office takes in the optional mode parameter. The default mode is the read mode.

                open("demo.txt", "r")              

If you want to check if a file can exist read, and so you can use the readable() method. This volition return a True or False.

                file.readable()              

The read() method is going to read all of the content of the file as one string.

                file.read()              

Once you lot are done reading a file, it is important that you shut it. If yous forget to close your file, and then that can crusade issues.

                file.shut()              

One way to ensure that your file is closed is to utilize the with keyword.

                with open up("demo.txt") as file:     print(file.read())              

The readline() method is going to read one line from the file and return that.

                file.readline()              

The readlines() method will read and return a list of all of the lines in the file.

                file.readlines()              

An alternative to these different read methods would exist to use a for loop.

                with open("demo.txt") as file:     for item in file:         print(particular)              

I hope you enjoyed this article and best of luck on your Python journey.

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