Python Topics : Reading and Writing Text Files
Opening a Text File
use the open() function 
# Open function to open the file "MyFile1.txt"
# (same directory) in append mode and
file1 = open("MyFile1.txt","a")

# store its reference in the variable file1
# and "MyFile2.txt" in D:\Text in file2
file2 = open(r"D:\Text\MyFile2.txt","w+")
file modes
ModeDescription
'r' open text file for reading
raises an I/O error if the file does not exist
'r+' open the file for reading and writing
raises an I/O error if the file does not exist
'w' open the file for writing
truncates the file if it already exists
creates a new file if it does not exist
'w+' open the file for reading and writing
truncates the file if it already exists
creates a new file if it does not exist
'a' open the file for writing
the data being written will be inserted at the end of the file
creates a new file if it does not exist
'a+' open the file for reading and writing
the data being written will be inserted at the end of the file
creates a new file if it does not exist
'rb' open the file for reading in binary format
raises an I/O error if the file does not exist
'rb+' open the file for reading and writing in binary format
raises an I/O error if the file does not exist
'wb' open the file for writing in binary format
truncates the file if it already exists
creates a new file if it does not exist
'wb+' open the file for reading and writing in binary format
truncates the file if it already exists
creates a new file if it does not exist
'ab' open the file for appending in binary format
inserts data at the end of the file
creates a new file if it does not exis.
'ab+' open the file for reading and appending in binary format
inserts data at the end of the file
creates a new file if it does not exis.
Reading a Text File
Reading from a File Using read()
.read() returns the read bytes in form of a string
reads n bytes
if no n specified, reads the entire file 
File_object.read([n])
Reading a Text File Using readline()
.readline() reads a line of the file and returns in form of a string
for specified n reads at most n bytes
does not reads more than one line, even if n exceeds the length of the line 
File_object.readline([n])
Reading a Text File Using readlines()
.readlines() reads all the lines and returns them as each line a string element in a list 
File_object.readlines()
'\n' is treated as a special character of two bytes
Writing a Text File
Writing to a Text File Using write()
.write() inserts a string str1 in a single line in the text file 
file = open("Employees.txt", "w") 

for i in range(3): 
name = input("Enter the name of the employee: ") 
file.write(name) 
# .write() does not add a newline
file.write("\n")  
file.close()
Writing to a Text File Using writelines()
writelines() writes a list of string elements to the file
each string is inserted in the text file individually
used to insert multiple strings at a single time 
file1 = open("Employees.txt", "w") 
lst = [] 
for i in range(3): 
    name = input("Enter the name of the employee: ") 
    lst.append(name + '\n') 
    
file1.writelines(lst) 
file1.close()
Appending to a Text File
use the append file mode 
file1 = open("myfile.txt", "a")  # append mode
file1.write("Today \n")
file1.close()
Closing a Text File
close() function closes the file
frees the memory space acquired by the file 
# Opening and Closing a file "MyFile.txt"
# for object name file1.
file1 = open("MyFile.txt","a")
file1.close()
index