does "for line in file" work with binary files in python?

I would write a simple helper function to read in the chunks you want:

def read_in_chunks(infile, chunk_size = 1024):
   while True:
   chunk = infile.read(chunk_size)
if chunk:
   yield chunk
else:
   # The chunk was empty, which means we 're at the end
# of the file
return

The use as you would for line in file like so:

with open(fn.
      'rb') as f:
   for chunk in read_in_chunks(f):
   # do you stuff on that chunk...

You can also do:

from collections
import partial
with open(fn, 'rb') as f:
   for chunk in iter(functools.partial(f.read, numBytes), ''):

Binary mode means that the line endings aren’t converted and that bytes objects are read (in Python 3); the file will still be read by “line” when using for line in f. I’d use read to read in consistent chunks instead, though.

with open(image_filename, 'rb') as f:
   # iter(callable, sentinel)– yield f.read(4096) until b ''
appears
for chunk in iter(lambda: f.read(4096), b ''): …

often with binary files you consume them in chunks

CHUNK_SIZE = 1024
for chunk in iter(lambda: fh.read(CHUNK_SIZE), ""):
   do_something(chunk)

Suggestion : 2

Note that it’s already possible to iterate on file objects using for line in file: ... without calling file.readlines().,Binary I/O (also called buffered I/O) expects bytes-like objects and produces bytes objects. No encoding, decoding, or newline translation is performed. This category of streams can be used for all kinds of non-text data, and also when manual control over the handling of text data is desired.,A custom opener can be used by passing a callable as opener. The underlying file descriptor for the file object is then obtained by calling opener with (name, flags). opener must return an open file descriptor (passing os.open as opener results in functionality similar to passing None).,The io module provides Python’s main facilities for dealing with various types of I/O. There are three main types of I/O: text I/O, binary I/O and raw I/O. These are generic categories, and various backing stores can be used for each of them. A concrete object belonging to any of these categories is called a file object. Other common terms are stream and file-like object.

f = open("myfile.txt", "r", encoding = "utf-8")

f = io.StringIO("some initial text data")

f = open("myfile.jpg", "rb")

f = io.BytesIO(b "some initial binary data: \x00\x01")

f = open("myfile.jpg", "rb", buffering = 0)

# May not work on Windows when non - ASCII characters in the file.
with open("README.md") as f:
   long_description = f.read()

Suggestion : 3

Updated on May 18th 2020

OutPut:

Enter Name: Jhonson
Enter Employee ID: 212['Jhonson', '212']

It is important to know how to open a file before knowing how to create a file and use it. To do any operation on a file, first we need to open that file.
We should use the open() function to open a file. The open() function accepts mainly two arguments, file name and open mode .

file = open('file name', 'open mode', 'buffering')

A file which is opened must be closed it's always a best practice to close a file using the close() method. If we did not close the file after our work gets finished the memory utilized by the file is not freed. That is the reason closing a file is highly recommended.
Syntax:

file.close()

OutPut From the SampleText.txt

Arjun
Software Employee
London
Joseph
Amith
Cena

Output

Is File Closed: False
IsFileClosed: True

file = open('file name', 'open mode', 'buffering')

file.close()

We know that data in the binary files is stored in the form of bytes. When we perform reading and writing operations on a binary file, a file pointer moves inside the file depending on the how many bytes are written or read from the file.
We use the tell() method to return current position of the cursor from the beginning of the file.
The position(index) of first character in files is zero just like string index.
Syntax for tell()

file.tell()

If we want to move the cursor/FilePointer to another positon we use seek()
Syntax for seek()

file.seek(offset, fromwhere)

We can use os library to get information about files in our computer.
os module has path sub module, which contains isFile() function to check whether a particular file exists or not?

os.path.isfile(fname)

Suggestion : 4

There are two types of files in Python - text files and binary files.,In above programs the open() function opens the oceans.txt file for reading, using the 'r' mode. The infile.read() method reads file content into memory as a string and assigned to the data variable.,open function creates the file 'oceans.txt' and returns the file object to outfile. 'w' is file mode used for writing to text file.,The readlines() returns a list of strings, each representing a single line of the file. If n is not provided then all lines of the file are returned.

The open function is used in Python to open a file. The open function returns a file object and associates it with a file on the disk. Here is the general format:

variable = open(filename, mode)

Program (oceans.py)

outfile = open('oceans.txt', 'w') #Step 1
outfile.write('Atlantic\n') #Step 2
outfile.write('Pacific\n')
outfile.write('Indian\n')
outfile.write('Arctic\n')
outfile.close() #Step 3

Step 1

outfile = open('oceans.txt', 'w') #Step 1

Step 3

outfile.close()

The writelines() method: writeline method takes an iterable as argument (an iterable object can be a tuple, a list). Each item contained in the iterator is expected to be a string. The above program can be made using writelines() method:

outfile = open('oceans.txt', 'w')
text = 'Atlantic\n', 'Pacific\n', 'Indian\n', 'Arctic\n'
outfile.writelines(text)
outfile.close()

Suggestion : 5

All of the preceding examples process simple text files. Python scripts can also open and process files containing binary data—JPEG images, audio clips, packed binary data produced by FORTRAN and C programs, and anything else that can be stored in files. The primary difference in terms of your code is the mode argument passed to the built-in open function:,The readlines method loads the entire contents of the file into memory and gives it to our scripts as a list of line strings that we can step through in a loop. In fact, there are many ways to read an input file:,[*] For instance, to process pipes, described in Chapter 5. The Python pipe call returns two file descriptors, which can be processed with os module tools or wrapped in a file object with os.fdopen.,The os module contains an additional set of file-processing functions that are distinct from the built-in file object tools demonstrated in previous examples. For instance, here is a very partial list of os file-related calls:

C: \temp > python >>>
   file = open('data.txt', 'w') # open output file object: creates >>>
   file.write('Hello file world!\n') # writes strings verbatim >>>
   file.write('Bye   file world.\n') >>>
   file.close() # closed on gc and exit too

file.writelines(['Hello file world!\n', 'Bye   file world.\n'])

open('somefile.txt', 'w').write("G'day Bruce\n")

>>> file = open('data.txt', 'r') # open input
file
object
   >>>
   for line in file.readlines(): # read into line string list
   ...print line, # lines have '\n'
at end
   ...
   Hello file world!
   Bye file world.

>>> file = open('data.txt') # open input file object >>>
   for line in file.readlines(): # read into line string list
   ...print line,

>>> file = open('data.txt', 'a') # open in append mode: doesn 't erase >>>
   file.write('The Life of Brian') # added at end of existing data >>>
   file.close() >>>
   >>>
   open('data.txt').read() # open and read entire file 'Hello file world!\nBye   file world.\nThe Life of Brian'

Suggestion : 6

The current working directory is a property that Python holds in memory at all times. There is always a current working directory, whether we're in the Python Shell, running our own Python script from the command line, etc.,The glob module is another tool in the Python standard library. It's an easy way to get the contents of a directory programmatically, and it uses the sort of wildcards that we may already be familiar with from working on the command line.,To open a file for writing, use the open() function and specify the write mode. There are two file modes for writing as listed in the earlier table:,However, Python handles line endings automatically by default. Python will figure out which kind of line ending the text file uses and and it will all the work for us.

The current working directory is a property that Python holds in memory at all times. There is always a current working directory, whether we're in the Python Shell, running our own Python script from the command line, etc.

>>>
import os
   >>>
   print(os.getcwd())
C: \Python32 >>>
   os.chdir('/test') >>>
   print(os.getcwd())
C: \test

os.path contains functions for manipulating filenames and directory names.

>>>
import os
   >>>
   print(os.path.join('/test/', 'myfile')) /
   test / myfile >>>
   print(os.path.expanduser('~'))
C: \Users\ K >>>
   print(os.path.join(os.path.expanduser('~'), 'dir', 'subdir', 'k.py'))
C: \Users\ K\ dir\ subdir\ k.py

Note: we need to be careful about the string when we use os.path.join. If we use "/", it tells Python that we're using absolute path, and it overrides the path before it:

>>>
import os
   >>>
   print(os.path.join('/test/', '/myfile')) /
   myfile

The glob module is another tool in the Python standard library. It's an easy way to get the contents of a directory programmatically, and it uses the sort of wildcards that we may already be familiar with from working on the command line.

>>>
import glob
   >>>
   os.chdir('/test') >>>
   import glob >>>
   glob.glob('subdir/*.py')['subdir\\tes3.py', 'subdir\\test1.py', 'subdir\\test2.py']

Every file system stores metadata about each file: creation date, last-modified date, file size, and so on. Python provides a single API to access this metadata. We don't need to open the file and all we need is the filename.

>>>
import os
   >>>
   print(os.getcwd())
C: \test >>>
   os.chdir('subdir') >>>
   print(os.getcwd())
C: \test\ subdir >>>
   metadata = os.stat('test1.py') >>>
   metadata.st_mtime
1359868355.9555483
   >>>
   import time >>>
   time.localtime(metadata.st_mtime)
time.struct_time(tm_year = 2013, tm_mon = 2, tm_mday = 2, tm_hour = 21,
      tm_min = 12, tm_sec = 35, tm_wday = 5, tm_yday = 33, tm_isdst = 0) >>>
   metadata.st_size
1844

Suggestion : 7

Last Updated : 20 Jul, 2021,GATE CS 2021 Syllabus

Output:

Eighth line
Ninth line
Tenth line