Writing to a file in Python
problem
In a program, the data are stored in memory (RAM) and are volatile. In this post we will see how to save (persist) some data so the program can later load them. The data will be stored in a text file.
SOLUTION
In Python, we can write to a file easily. Let’s suppose we have the following string variable:
message = "this is a test line to be saved in a text file."
Let’s try to save the contents of the variable into a file. For instance the file will be named “message.txt”. We don’t need to create it beforehand in this case. In order to save the message variable above, we can do so as follows:
file = open("message.txt", "w") #create the file (or overwrite if exists)
file.write(message) #the contents of message variable
file.close() #close the file
running
After running the code above you should see the file created in the current path (same folder with the code file)
When we deal with files, there are always 3 steps.
- Open the file
- Do stuff e.g. write some contents
- Close the file
It’s very important to close the file afterwards.
File modes
At the moment we use the open() command, we specify the mode to be used. In this case we used “w” which signals for “write mode”.
Reading a file:
If the file existed already and we wanted to simply read its content we would have used the “r” mode which is the “read mode”.
Some of the other modes:
“w” – Write mode
“r” – Read mode
“a” – Append mode
“x” – open for exclusive creation, if the file already exists it will return an error
conclusion
In this post we saw how to easily write to a file using Python. This is an example of a persistent memory. You can write a program that later reads that file and makes use of the date.
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Ellion
Professional IT consultant, writer, programmer enthusiast interested in all sorts of coding.
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