Python IO Programming--File read/write

1.1   file read/write1.1.1   Read the file

>>> f = open ('/root/python/hello.py ', ' R ') # identifier r denotes read

>>> f =open ('/root/python/hello1.py ', ' R ') # file does not exist error

Traceback (most recent):

File "<stdin>", line 1, in <module>

Filenotfounderror: [Errno 2] No such fileor directory: '/root/python/hello1.py '

Read File contents

>>> f.read () #str Object

"#!/usr/bin/python\nprint (' Hello,world ') \ n"

>>> F.close () # Close File

file invocation may result in read and write IOError, once the error F.close () will not be called, then we use the following statement:

>>> Try:

... f = open ('/root/python/hello.py ', ' R ')

... print (F.read ())

... finally:

... if f:

... f.close ()

...

#!/usr/bin/python

Print (' Hello,world ')

Python provides us with a much simpler approach.

>>> withopen ('/root/python/hello.py ', ' R ') as F:

... print (F.read ())

...

#!/usr/bin/python

Print (' Hello,world ')

Attention:

Read () reads the entire contents of the file at once, using smaller files;

Read (size) reads the contents of a size byte at most, and does not determine the size of the file;

ReadLine () can read one line at a time, call ReadLines () to read all the content at once and return the list by row , for the configuration file.

>>> withopen ('/root/python/hello.py ', ' R ') as F:

... For line in F.readlines ():

... print (Line.strip ())

...

#!/usr/bin/python

Print (' Hello,world ')

1.1.2   File-like Object

like the Open () function , this object, which has a read () method, is called File-like object in Python. file-like Object does not require inheritance from a particular class, just write a read () method on the line.

1.1.3   Binary Files

The default is to read the text file, and it is a UTF-8 encoded text file. To read binary files, compare slices, videos, etc., open the file with ' RB ' mode.

>>> f =open ('/users/michael/test.jpg ', ' RB ')

>>> F.read ()

B ' \xff\xd8\xff\xe1\x00\x18exif\x00\x00 ... ' # hexadecimal representation of bytes

1.1.4   character encoding

to read non- UTF-8 encoded text file, need to give the open () function incoming encoding parameter, for example, read GBK encoded file:

>>> f =open ('/users/michael/gbk.txt ', ' R ', encoding= ' GBK ')

>>> F.read ()

' test '

You may encounter some files that are not code-compliant Unicodedecodeerror, because there may be some characters that are illegally encoded in a text file. In this case,the open () function also receives a errors parameter that indicates what to do if a coding error is encountered. The simplest way is to ignore it directly:

>>> f =open ('/users/michael/gbk.txt ', ' R ', encoding= ' GBK ', errors= ' ignore ')

1.1.5   Write a file

Python does not require the destination file to exist when writing files.

[[email protected] python]# ls test.txt

Test.txt

[Email protected] python]# rm-f test.txt

[[email protected] python]# python

Python 3.5.0b4 (default, Jul 1 2016, 21:28:36)

[GCC 4.1.2 20080704 (Red Hat 4.1.2-48)] Onlinux

Type "Help", "copyright", "credits" or "license" for moreinformation.

>>> f = open ('/root/python/test.txt ', ' W ') #w means write text file,WB means write binary file

>>> f.write (' hello,python! ')

14

>>> F.close ()

>>>

[email protected] python]# cat Test.txt

Hello, python!.

Write again on the same file will overwrite

>>> withopen ('/root/python/test.txt ', ' W ') as F: # can also encoding specified character encoding

... f.write (' abc ')

... f.write (' 123 ')

...

3

3

>>>

[Email protected] python]#

[email protected] python]# cat Test.txt

abc123 [[email protected] python]# python

Python 3.5.0b4 (default, Jul 1 2016, 21:28:36)

[GCC 4.1.2 20080704 (Red Hat 4.1.2-48)] Onlinux

Type "Help", "copyright", "credits" or "license" for moreinformation.

>>> withopen ('/root/python/test.txt ', ' W ') as F:

... f.write (' NEW ')

...

3

>>>

[Email protected] python]#

[email protected] python]# cat Test.txt

NEW

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Python IO Programming--File read/write