Reading and writing binary files in python
The advantage to using this method is that the related code is both simple and easy to read. This method is used to add information or content to an existing file. To start a new line after you write data to the file, you can add an EOL character.
Obviously, this will amend our current file to include the two new lines of text. What this does is close the file completely, terminating resources in use, in turn freeing them up for the system to deploy elsewhere. Notice how we have used this in several of our examples to end interaction with a file?
This is good practice. Feel free to copy the code and try it out for yourself in a Python interpreter make sure you have any named files created and accessible first. You can also work with file objects using the with statement. It is designed to provide much cleaner syntax and exceptions handling when you are working with code. One bonus of using this method is that any files opened will be closed automatically after you are done.
This leaves less to worry about during cleanup. You can also call upon other methods while using this statement. For instance, you can do something like loop over a file object:. What this is designed to do, is split the string contained in variable data whenever the interpreter encounters a space character. You can actually split your text using any character you wish - such as a colon, for instance.
If you wanted to use a colon instead of a space to split your text, you would simply change line. The reason the words are presented in this manner is because they are stored — and returned — as an array. Be sure to remember this when working with the split function. For Python training , our top recommendation is DataCamp. Datacamp provides online interactive courses that combine interactive coding challenges with videos from top instructors in the field.
It's very nice tutorial. But is there any way to extract word by instead of line by line from the file. I mean after getting the entire string we can take it as string and can slice as list but other than this method. I'm in Windows, but I figured it out! I just had to take out the extra spaces at the end of every line in the text I'm trying to read. It is possible that your code is well, but the text file you are trying to read can have multiple linebreaks or mixed linebreaks like.
Which operating system do you use? Whenever I open a file and use my "for line in file" statement to print the lines of my file, it prints a line, then a blank line, then a line, then a blank one, etc The open function opens a file. When you use the open function, it returns something called a file object. File objects contain methods and attributes that can be used to collect information about the file you opened. They can also be used to manipulate said file.
For example, the mode attribute of a file object tells you which mode a file was opened in. And the name attribute tells you the name of the file that the file object has opened. You must understand that a file and file object are two wholly separate — yet related — things.
The second way is to use the str. The string module contains a Template class which offers yet another way to substitute values into strings. One question remains, of course: Luckily, Python has ways to convert any value to a string: The str function is meant to return representations of values which are fairly human-readable, while repr is meant to generate representations which can be read by the interpreter or will force a SyntaxError if there is no equivalent syntax. Many values, such as numbers or structures like lists and dictionaries, have the same representation using either function.
Strings and floating point numbers, in particular, have two distinct representations. Note that in the first example, one space between each column was added by the way print works: This example demonstrates the str. There are similar methods str. These methods do not write anything, they just return a new string.
If you really want truncation you can always add a slice operation, as in x. There is another method, str. It understands about plus and minus signs:. Basic usage of the str. The brackets and characters within them called format fields are replaced with the objects passed into the str. A number in the brackets refers to the position of the object passed into the str.
If keyword arguments are used in the str. This allows greater control over how the value is formatted. The following example rounds Pi to three places after the decimal. Passing an integer after the ': This is useful for making tables pretty. This can be done by simply passing the dict and using square brackets '' to access the keys.
This is particularly useful in combination with the built-in function vars , which returns a dictionary containing all local variables. For a complete overview of string formatting with str.
It interprets the left argument much like a sprintf -style format string to be applied to the right argument, and returns the string resulting from this formatting operation.
More information can be found in the String Formatting Operations section. The first argument is a string containing the filename. The second argument is another string containing a few characters describing the way in which the file will be used. Python on Windows makes a distinction between text and binary files; the end-of-line characters in text files are automatically altered slightly when data is read or written.
Be very careful to use binary mode when reading and writing such files. The rest of the examples in this section will assume that a file object called f has already been created. Otherwise, at most size bytes are read and returned. If the end of the file has been reached, f.
This makes the return value unambiguous; if f. For reading lines from a file, you can loop over the file object. This is memory efficient, fast, and leads to simple code:. If you want to read all the lines of a file in a list you can also use list f or f. It is good practice to use the with keyword when dealing with file objects.
This has the advantage that the file is properly closed after its suite finishes, even if an exception is raised on the way.