Loop through files with for

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: open 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 +)

To view help:

open(...)

open(name[, mode[, buffering]]) -> file object

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

preferred way to open a file.  See file.__doc__ for further information.

(END)...skipping...



[root[@localhost](https://my.oschina.net/u/570656) ~]# cat /tmp/1.txt

1111

[root[@localhost](https://my.oschina.net/u/570656) ~]#

Open read only:

In [26]: open('/tmp/1.txt')

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

In [27]: fd = open('/tmp/1.txt')

In [28]: fd

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

In [29]: type(fd)

Out[29]: file

Open as write:

In [34]: fd = open('/tmp/1.txt','w')

In [35]: fd.write('2222\n')

In [36]: fd.close()

[root[@localhost](https://my.oschina.net/u/570656) ~]# cat /tmp/1.txt

2222

[root[@localhost](https://my.oschina.net/u/570656) ~]#

Open as append:

In [34]: fd = open('/tmp/1.txt','a')

In [35]: fd.write('3333\n')

In [36]: fd.close()

[root[@localhost](https://my.oschina.net/u/570656) ~]# cat /tmp/1.txt

2222

3333

[root@localhost ~]#

read():

In [41]: fd.read()

Out[41]: '2222\n3333\n'

In [42]: fd.read()

Out[42]: ''

In [49]: fd.readline()

Out[49]: '2222\n'

In [50]: fd.readline()

Out[50]: '3333\n'

In [51]: fd.readline()

Out[51]: ''

In [52]:

read() and readline() return strings:

readlines() returns a list:

in [52]: fd = open('/tmp/1.txt')

In [53]: 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()



[root@localhost 20171228]# python read_file.py22223333[root@localhost 20171228]#

Loop through files using while

Script:

#!/usr/bin/python
fd = open('/tmp/1.txt')
while True:

    line = fd.readline()
    if not line:
        break
    print line,

fd.close()



[root@localhost 20171228]# python read_fi_while.py
22223333
[root@localhost 20171228]#

To open a file with open:

#!/usr/bin/python
with open('/tmp/1.txt') as fd:
while True:

    line = fd.readline()
    if not line:
        break
print line,