File Handling
File Handling in Python
File handling allows to store data permanently, later retrieve it. This is usually used for saving records, logs, configurations, or user data.
Opening a File
Python uses the open() function to work with files.
file = open("filename","mode")
File Modes
- r : Read
- w : Write(creates new file or overwrites existing)
- a : Append (adds data at the end)
- x : Create (error if file exists)
- rb / wb : Read/Write in binary mode
Writing to a File
file = open("records.txt","w")
file.write("Hello, this is Python file handling.\n")
file.write("Writing to a file.")
file.close()
Using with
with open("records_i.txt","w") as file:
file.write("File will be close automatically!")
file.write("No need to call close method.")
Reading from a file
with open("records_i.txt","r") as file:
content = file.read()
print(content)
Reading Line by Line
with open("records_i.txt","r") as file:
for l in file:
print(l.strip())
Reading one Line
file = open("records_i.txt","r")
print("Line:: ".file.readline())
file.close()
Appending to a File
with open("records_i.txt","a") as file:
file.write("\nThis line will be added to file, old content will not be erased.")
Examples to work with custom function
def writeToFile():
file = open("data.txt", "a")
file.write("Writing to file using python code")
file.close()
def readFromFile():
file = open("data.txt", "r")
data = file.read()
print(data)
def writeToFile2():
with open("data_2.txt", "w") as file:
file.write("Writing to file using python code")
file.write("\nHello this will appear in next line")
file.write("\nThis will appear in third line")
file.close()
def readFromFile2():
with open("data_2.txt","r") as file:
for line in file.read():
print(line,end="")
with open("test.txt", 'r') as f:
print(f.mode())
f_contents = f.readline()
print(f_contents,end="")
for line in f:
print(line,end="")
size_to_read = 10
print(f.tell())
f.seek(0) #begining
while len(f_contents) > 0:
print(f_contents,end="")
f_contents = f.read(size_to_read)
with open("test.txt", 'w') as f:
f.write("Hello")
f.seek(0)
f.write("World")
with open("test.jpg", 'w') as f:
with open("test_copy.jpg","w") as wf:
for line in f:
wf.write(line)
Example: random access
with open("test.txt", 'r') as f:
print("File is opened in Mode: ",f.mode)
f_contents = f.readline()
print(f_contents,end="")
for line in f:
print(line,end="")
print("\nCursor Position: ",f.tell())
f.seek(0) #begining
print("\nCursor Position: ", f.tell())
#while len(f_contents) > 0:
# print(f_contents,end="")
size_to_read = 10 #size of data to read
f_contents = f.read(size_to_read) #reading only first 10 bytes
print("\nFile Contents: ",f_contents)
with open("test.text", 'w') as f:
f.write("Hello") #writing Hello to fine
f.seek(0) # bringing cursor to 0 th position
f.write("World") # write World at 0 th position
with open("test.jpg", 'r') as f:
with open("test_copy.jpg","w") as wf:
for line in f:
wf.write(line)