Python startswith and then look a word in a conditional block

Question

I have below working code which works fine, but just looking way around if there is an another elegant way of doing this, because here i'm using else condition to print the last line or dataBlock to be printed.

Note: mydudalt1 and mydudalt2 are the host names

My data File:

$ cat mydata_test.txt
-- mydudalt1 --
 192.168.2.40; // udalt-sanjose
 192.168.2.56; // udalt-sj1
 192.168.98.71; // udalt-japan
 192.168.2.146; //udalt-sj-fwd1
-- mydudalt2 --
 199.43.4.70; // udalt-chelms
 192.168.2.56; // udalt-sj1
 192.168.98.71; // udalt-japan

My Working code:

#!/grid/common/pkgs/python/v3.6.1/bin/python3
dataBlock = ''
with open('mydata_test.txt', 'r') as frb:
 for line in frb:
 line = line.strip("\n")
 if line.startswith('--'):
 if "japan" in dataBlock:
 print(dataBlock)
 dataBlock = ''
 dataBlock = dataBlock + line
 elif "japan" in line:
 dataBlock = dataBlock + line
 else:
 print(dataBlock + line)

Resulted Output:

-- mydudalt1 -- 192.168.98.71; // udalt-japan
-- mydudalt2 -- 192.168.98.71; // udalt-japan

• kushj: Can mydudalt blocks have more than one JAPAN Ids in them?
• Karn Kumar: @kushj, no. mydudalt1 and mydudalt2 are the host names.

Answer 1

If "japan" only appears once in each section, you can store the startswith line, and simply print out the desired output immediately when the matching line is found:

for line in frb:
 line = line.strip("\n")
 if line.startswith("--"):
 prefix = line
 if "japan" in line:
 print(prefix + line)

• Karn Kumar: AJNeufeld, this looks to be neat and promising +1, thnx

Answer 2

Unless there is an indentation issue,

 dataBlock = ''
 dataBlock = dataBlock + line

can be written:

 dataBlock = line

• Karn Kumar: Josay, that will not do the job because if i will use dataBlock = line instead of dataBlock = dataBlock + line then it will not print host names. +1 for the throwing an idea

Answer 3

A quick Answer [Should not be used in PRODUCTION]

I mainly try to answer your concern over how to avoid "for-else" to handle last edge case, and haven't reviewed much of rest of code.

#!/grid/common/pkgs/python/v3.6.1/bin/python3
block_start_identifier = "--"
search_word = "japan"
data_block = []
block_satisfied = False
with open('mydata_test.txt', 'r') as frb:
 for line in frb.readlines():
 if line.startswith(block_start_identifier):
 # Print previous blocks
 if block_satisfied:
 print("".join(data_block))
 # Reset data blocks
 data_block = []
 block_satisfied = False
 data_block.append(line)
 elif search_word in line:
 data_block.append(line)
 block_satisfied = True
# Flush the block again as needed to handle last case
if block_satisfied:
 print("".join(data_block))
```

• Karn Kumar: kushj, thnx for the answer. +1 for the approach around.