Python open reading and writing files to implement script code display

File operations in Python can be done through the open function, which is indeed very similar to fopen in C language. Obtain a file object through the open function, and then call read(), write() and other methods to read and write the file.

1.open

After using open to open a file, you must remember to call the close() method of the file object. For example, you can use the try/finally statement to ensure that the file can be closed finally.

file_object = open('thefile.txt')
try:
  all_the_text = file_object.read( )
finally:
  file_object.close( )

Note: The open statement cannot be placed in the try block, because when an exception occurs when opening the file, the file object file_object cannot execute the close() method.

2. Read files

Read text files

input = open('data', 'r')
#第二个参数默认为r
input = open('data')

Read binary files

input = open('data', 'rb')

Read all contents

file_object = open('thefile.txt')
try:
  all_the_text = file_object.read( )
finally:
  file_object.close( )

Read fixed bytes

file_object = open('abinfile', 'rb')
try:
  while True:
    chunk = file_object.read(100)
    if not chunk:
      break
    do_something_with(chunk)
finally:
  file_object.close( )

Read each line

list_of_all_the_lines = file_object.readlines( )

If the file is a text file, you can also directly traverse the file object to obtain each line:

for line in file_object:
    process line

3. Write file

Write text file

output = open('data', 'w')

Write binary file

output = open('data', 'wb')

Append write file

output = open('data', 'w+')

Write Data

file_object = open('thefile.txt', 'w')
file_object.write(all_the_text)
file_object.close( )

Write multiple lines

file_object.writelines(list_of_text_strings)

Note that calling writelines to write multiple lines will have higher performance than using write to write in one go.

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