Iterating through a file instance in Python using the For,while loop

traversing a file with a for loop

Open File

Open

r: Open in read mode

w: Open in write mode

A: Open in Append mode

r+: Open in read-write mode

w+: Open in read/write mode (see W)

A +: Open in read/write mode (see a)

RB: Open in binary read mode

WB: Opens in binary write mode (see W)

AB: Open in binary append mode (see a)

rb+: Open in binary read/write mode (see r+)

wb+: Open in binary read/write mode (see w+)

ab+: Open in binary read/write mode (see A +)

View Help:

Open (...)

Open (name[, mode[, buffering]), file object

Open a file using the file () type, returns a file object. The

Preferred to open a file. See file.__doc__ for further information.

(END) ... skipping ...

[Email protected] ~]# Cat/tmp/1.txt

1111

[Email protected] ~]#

Read-only mode open:

in [+]: Open ('/tmp/1.txt ')

OUT[26]: <open file '/tmp/1.txt ', mode ' R ' at 0x20860c0>

in [+]: FD = open ('/tmp/1.txt ')

in [+]: FD

OUT[28]: <open file '/tmp/1.txt ', mode ' R ' at 0x20861e0>

In []: type (FD)

OUT[29]: File

Open in write mode:

in [+]: FD = open ('/tmp/1.txt ', ' W ')

in [+]: fd.write (' 2222\n ')

In [approx]: Fd.close ()

[Email protected] ~]# Cat/tmp/1.txt

2222

[Email protected] ~]#

Open in Append mode:

in []: FD = open ('/tmp/1.txt ', ' a ')

in [+]: fd.write (' 3333\n ')

In [approx]: Fd.close ()

[Email protected] ~]# Cat/tmp/1.txt

2222

3333

[Email protected] ~]#

Read ():

in [+]: Fd.read ()

OUT[41]: ' 2222\n3333\n '

In [All]: Fd.read ()

OUT[42]: "

in [+]: Fd.readline ()

OUT[49]: ' 2222\n '

in [[]: Fd.readline ()

OUT[50]: ' 3333\n '

In [Wuyi]: Fd.readline ()

OUT[51]: "

In [52]:

Read () and ReadLine () return a string:

ReadLines () returns the list:

in [*]: FD = open ('/tmp/1.txt ')

in [+]: Fd.readlines ()

OUT[53]: [' 2222\n ', ' 3333\n ']

Script:

#!/usr/bin/python

FD = open ('/tmp/1.txt ')

For line in FD:

Print line,

Fd.close ()

[email protected] 20171228]# python read_file.py

2222

3333

[Email protected] 20171228]#

Traversing a file using a while loop

Script:

#!/usr/bin/python

FD = open ('/tmp/1.txt ')

While True:

line = Fd.readline ()

If not line:

Break

Print line,

Fd.close ()

[email protected] 20171228]# python read_fi_while.py

2222

3333

[Email protected] 20171228]#

With open file:

#!/usr/bin/python

With open ('/tmp/1.txt ') as FD:

While True:

line = Fd.readline ()

If not line:

Break

Print line,

Iterating through a file instance in Python using the For,while loop