Python for Network Engineers Week#2

Python for Network Engineers Week 2

Reading from a File

Open file for reading, use the .read() method to read in the entire file as a string. Finally, close the file. Note the file is in the same directory.

(Python4Networking) (base) pradeep:~$cat file-reading-1.py 
f1=open("junos-config.txt")
print (type(f1))
my_config=f1.read()
print(type(my_config))
f1.close()
print(my_config)
(Python4Networking) (base) pradeep:~$

(Python4Networking) (base) pradeep:~$python3 file-reading-1.py 
<class '_io.TextIOWrapper'>
<class 'str'>
root@srx1> show configuration | display set 
set system host-name srx1
set system root-authentication encrypted-password "$1$nq.N1UsY$JxA/ESAj3KuXseXE597gg0"
set system root-authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDS8VmjJwq5I7swH3/Uh6UIecpz4AXF3WGMWTZQUP2TpKxA6cRfMbjnS3WgMpsjWwiM67n5/5ONfeLRwMerFyLTEPRZZhUOpk7PRInUHXOQ9n25eeOwxXA2RyD5FHmlmBnr1zf38Yq2Za+zR0PmY2k7KBb4EILfAeOcJnIj4IurQWJvf0mt1dQzqkRj6nT7c3q5849NUlL+S2sDjCBI/0UqZbX1dic1i1IwXALuvNz2ZWhROQRzQf21+ZiwKFqfI3A5asMrTZDI7Cfy9VNrK4BeCJOAcZJHGTgleusYZGnq05ZQQY0U/htw3FQ2Rkj+nKgAGSza6/2Mi6mBuIyzk/0P vagrant"
set system login user vagrant uid 2000
set system login user vagrant class super-user
set system login user vagrant authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA6NF8iallvQVp22WDkTkyrtvp9eWW6A8YVr+kz4TjGYe7gHzIw+niNltGEFHzD8+v1I2YJ6oXevct1YeS0o9HZyN1Q9qgCgzUFtdOKLv6IedplqoPkcmF0aYet2PkEDo3MlTBckFXPITAMzF8dJSIFo9D8HfdOV0IAdx4O7PtixWKn5y2hMNG0zQPyUecp4pzC6kivAIhyfHilFR61RGL+GPXQ2MWZWFYbAGjyiYJnAmCP3NOTd0jMZEnDkbUvxhMmBYSdETk1rRgm+R4LOzFUGaHqHDLKLX+FIPKcF96hrucXzcWyLbIbEgE98OHlnVYCzRdK8jlqm8tehUc9c9WhQ== vagrant insecure public key"
set system services ssh root-login allow
set system services netconf ssh
set system services web-management http interface ge-0/0/0.0
set system syslog user * any emergency
set system syslog file messages any any
set system syslog file messages authorization info
set system syslog file interactive-commands interactive-commands any
set system license autoupdate url https://ae1.juniper.net/junos/key_retrieval
set interfaces ge-0/0/0 unit 0 family inet dhcp
set interfaces ge-0/0/1 unit 0 family inet address 192.168.1.1/24
set security forwarding-options family inet6 mode packet-based
set security forwarding-options family mpls mode packet-based

root@srx1> 

(Python4Networking) (base) pradeep:~$

Note the type of input and output, at the top. Defaults to text file and read mode. These settings can be changed.

Another way, using readline() method, to read each line, line by line.

(Python4Networking) (base) pradeep:~$python3
Python 3.9.12 (main, Apr  5 2022, 01:53:17) 
[Clang 12.0.0 ] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> f1 = open("junos-config.txt")
>>> f1
<_io.TextIOWrapper name='junos-config.txt' mode='r' encoding='UTF-8'>
>>> f1.readline()
'root@srx1> show configuration | display set \n'
>>> f1.readline()
'set system host-name srx1\n'
>>> f1.readline()
'set system root-authentication encrypted-password "$1$nq.N1UsY$JxA/ESAj3KuXseXE597gg0"\n'
>>> f1.readline()
'set system root-authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDS8VmjJwq5I7swH3/Uh6UIecpz4AXF3WGMWTZQUP2TpKxA6cRfMbjnS3WgMpsjWwiM67n5/5ONfeLRwMerFyLTEPRZZhUOpk7PRInUHXOQ9n25eeOwxXA2RyD5FHmlmBnr1zf38Yq2Za+zR0PmY2k7KBb4EILfAeOcJnIj4IurQWJvf0mt1dQzqkRj6nT7c3q5849NUlL+S2sDjCBI/0UqZbX1dic1i1IwXALuvNz2ZWhROQRzQf21+ZiwKFqfI3A5asMrTZDI7Cfy9VNrK4BeCJOAcZJHGTgleusYZGnq05ZQQY0U/htw3FQ2Rkj+nKgAGSza6/2Mi6mBuIyzk/0P vagrant"\n'
>>> 

To go to the beginning of the file, use the seek method with a value of 0.

To read all of the lines of a file as a list, use the readlines()method. Note the plural usage here.

>>> f1.seek(0)
0
>>> my_config=f1.readlines()
>>> type(my_config)
<class 'list'>
>>> print(my_config)
['root@srx1> show configuration | display set \n', 'set system host-name srx1\n', 'set system root-authentication encrypted-password "$1$nq.N1UsY$JxA/ESAj3KuXseXE597gg0"\n', 'set system root-authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDS8VmjJwq5I7swH3/Uh6UIecpz4AXF3WGMWTZQUP2TpKxA6cRfMbjnS3WgMpsjWwiM67n5/5ONfeLRwMerFyLTEPRZZhUOpk7PRInUHXOQ9n25eeOwxXA2RyD5FHmlmBnr1zf38Yq2Za+zR0PmY2k7KBb4EILfAeOcJnIj4IurQWJvf0mt1dQzqkRj6nT7c3q5849NUlL+S2sDjCBI/0UqZbX1dic1i1IwXALuvNz2ZWhROQRzQf21+ZiwKFqfI3A5asMrTZDI7Cfy9VNrK4BeCJOAcZJHGTgleusYZGnq05ZQQY0U/htw3FQ2Rkj+nKgAGSza6/2Mi6mBuIyzk/0P vagrant"\n', 'set system login user vagrant uid 2000\n', 'set system login user vagrant class super-user\n', 'set system login user vagrant authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA6NF8iallvQVp22WDkTkyrtvp9eWW6A8YVr+kz4TjGYe7gHzIw+niNltGEFHzD8+v1I2YJ6oXevct1YeS0o9HZyN1Q9qgCgzUFtdOKLv6IedplqoPkcmF0aYet2PkEDo3MlTBckFXPITAMzF8dJSIFo9D8HfdOV0IAdx4O7PtixWKn5y2hMNG0zQPyUecp4pzC6kivAIhyfHilFR61RGL+GPXQ2MWZWFYbAGjyiYJnAmCP3NOTd0jMZEnDkbUvxhMmBYSdETk1rRgm+R4LOzFUGaHqHDLKLX+FIPKcF96hrucXzcWyLbIbEgE98OHlnVYCzRdK8jlqm8tehUc9c9WhQ== vagrant insecure public key"\n', 'set system services ssh root-login allow\n', 'set system services netconf ssh\n', 'set system services web-management http interface ge-0/0/0.0\n', 'set system syslog user * any emergency\n', 'set system syslog file messages any any\n', 'set system syslog file messages authorization info\n', 'set system syslog file interactive-commands interactive-commands any\n', 'set system license autoupdate url https://ae1.juniper.net/junos/key_retrieval\n', 'set interfaces ge-0/0/0 unit 0 family inet dhcp\n', 'set interfaces ge-0/0/1 unit 0 family inet address 192.168.1.1/24\n', 'set security forwarding-options family inet6 mode packet-based\n', 'set security forwarding-options family mpls mode packet-based\n', '\n', 'root@srx1> \n']
>>> 

As you can see now, my_config is a list now, with each line of the config as a list item.

>>> len(my_config)
21
>>> 

>>> dir(f1)
['_CHUNK_SIZE', '__class__', '__del__', '__delattr__', '__dict__', '__dir__', '__doc__', '__enter__', '__eq__', '__exit__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__lt__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_checkClosed', '_checkReadable', '_checkSeekable', '_checkWritable', '_finalizing', 'buffer', 'close', 'closed', 'detach', 'encoding', 'errors', 'fileno', 'flush', 'isatty', 'line_buffering', 'mode', 'name', 'newlines', 'read', 'readable', 'readline', 'readlines', 'reconfigure', 'seek', 'seekable', 'tell', 'truncate', 'writable', 'write', 'write_through', 'writelines']
>>> 

Third method is looping over the lines in the file.

>>> f1=open("junos-config.txt")
>>> for line in f1:
...     print(line)
... 
root@srx1> show configuration | display set 

set system host-name srx1

set system root-authentication encrypted-password "$1$nq.N1UsY$JxA/ESAj3KuXseXE597gg0"

set system root-authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDS8VmjJwq5I7swH3/Uh6UIecpz4AXF3WGMWTZQUP2TpKxA6cRfMbjnS3WgMpsjWwiM67n5/5ONfeLRwMerFyLTEPRZZhUOpk7PRInUHXOQ9n25eeOwxXA2RyD5FHmlmBnr1zf38Yq2Za+zR0PmY2k7KBb4EILfAeOcJnIj4IurQWJvf0mt1dQzqkRj6nT7c3q5849NUlL+S2sDjCBI/0UqZbX1dic1i1IwXALuvNz2ZWhROQRzQf21+ZiwKFqfI3A5asMrTZDI7Cfy9VNrK4BeCJOAcZJHGTgleusYZGnq05ZQQY0U/htw3FQ2Rkj+nKgAGSza6/2Mi6mBuIyzk/0P vagrant"

set system login user vagrant uid 2000

set system login user vagrant class super-user

set system login user vagrant authentication ssh-rsa "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA6NF8iallvQVp22WDkTkyrtvp9eWW6A8YVr+kz4TjGYe7gHzIw+niNltGEFHzD8+v1I2YJ6oXevct1YeS0o9HZyN1Q9qgCgzUFtdOKLv6IedplqoPkcmF0aYet2PkEDo3MlTBckFXPITAMzF8dJSIFo9D8HfdOV0IAdx4O7PtixWKn5y2hMNG0zQPyUecp4pzC6kivAIhyfHilFR61RGL+GPXQ2MWZWFYbAGjyiYJnAmCP3NOTd0jMZEnDkbUvxhMmBYSdETk1rRgm+R4LOzFUGaHqHDLKLX+FIPKcF96hrucXzcWyLbIbEgE98OHlnVYCzRdK8jlqm8tehUc9c9WhQ== vagrant insecure public key"

set system services ssh root-login allow

set system services netconf ssh

set system services web-management http interface ge-0/0/0.0

set system syslog user * any emergency

set system syslog file messages any any

set system syslog file messages authorization info

set system syslog file interactive-commands interactive-commands any

set system license autoupdate url https://ae1.juniper.net/junos/key_retrieval

set interfaces ge-0/0/0 unit 0 family inet dhcp

set interfaces ge-0/0/1 unit 0 family inet address 192.168.1.1/24

set security forwarding-options family inet6 mode packet-based

set security forwarding-options family mpls mode packet-based



root@srx1> 

>>>