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Learning Python- Intermediate course: Day 37, File handling in Python
Many times we need to save data into files for long-term usage. Today we will learn how to write data into a file and retrieve it.
Python has two types of files, text and binary. But we will now learn only about text files, which are quite popular.
How will the interpreter know when to end a line? Each line in a file has the EOL terminating character (example comma or newline character) which the interpreter reads and processes a new line..
We can open a file into four modes
If not passed, then Python will assume it to be “ r ” by default.
Syntax for opening a file We can open a file using the syntax
file = open('myfile.txt', 'r') # Reading mode
file = open('myfile.txt', 'a') # Writing mode
file = open('myfile.txt', 'w') # Appending mode
file = open('myfile.txt', 'r+') # Both reading and writingNote than the file name is case sensitive. So myfile.txt is not equal to Myfile.txt
First we make a file named....say
myfile.txtA Quick brown fox jumps over the lazy dog
Welcome to PYTHON ProgrammingIn case the file doesn't exist, we get this error-
Traceback (most recent call last):
File "main.py", line 1, in <module>
file = open("myfile.txt", "r")
FileNotFoundError: [Errno 2] No such file or directory: 'myfile.txt'We can read the contents of the file using the
file.read() methodfile = open("myfile.txt", "r")
print (file.read())OUTPUT
A Quick brown fox jumps over the lazy dog
Welcome to PYTHON ProgrammingWe can also return a specific number of characters by adding parameters to the read method. For example
file = open("myfile.txt", "r")
print (file.read(7))OUTPUT
A QuickThe value returned is a string
file = open("myfile.txt", "r")
print (type(file.read(7)))<class 'str'>We can access the file line by line using the for in loop
file = open("myfile.txt", "r")
for temp in file:
print (temp)This syntax prints out each element of the file in lines.
A Quick brown fox jumps over the lazy dog
Welcome to PYTHON ProgrammingWhen we write into a file, we do not need to create one. If the file in which we want to write doesn't exist, it gets automatically created.
file = open('myfile.txt','w')
file.write("A Quick brown fox jumps over the lazy dog.")
file.write("Welcome to PYTHON Programming")
file.close()OUTPUT (myfile.txt)
A Quick brown fox jumps over the lazy dog.Welcome to PYTHON ProgrammingThe close() command terminates all the resources in use and frees the system of this particular program.
If we want the text into two separate lines, we can use the newline
\n symbol.file = open('myfile.txt','w')
file.write("A Quick brown fox jumps over the lazy dog.")
file.write("\n")
file.write("Welcome to PYTHON Programming")
file.close()OUTPUT- (myfile.txt)
A Quick brown fox jumps over the lazy dog.
Welcome to PYTHON ProgrammingThe write method overrides the file each and every time the file is opened function is called. To avoid this, we can use the append mode to add to the file.
file = open('myfile.txt','a')
file.write("A Quick brown fox jumps over the lazy dog.")
file.write("\n")
file.write("Welcome to PYTHON Programming")
file.close()A Quick brown fox jumps over the lazy dog.
Welcome to PYTHON ProgrammingA Quick brown fox jumps over the lazy dog.
Welcome to PYTHON ProgrammingSo friends we have covered file handling today. From next parts onwards we will cover object oriented programming.
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