[ reading lines starting specifically with some criteria ]
I have a huge data file: I need to extract lines starting with say U(1.0 ----) irrespective of the line number because the line number varies with each run.
I tried splitting and reading but the output is not handleable. Can anyone help me?
Answer 1
- you have to read a file (https://docs.python.org/2/tutorial/inputoutput.html#reading-and-writing-files)
- Then make a loop though lines and get the first part of the line.
- Then you need to check if match with a regular expression you design for that task.
Hope it helps you :)
Answer 2
Use the startswith() string method on each line and add them to a seperate list for analysis
data = open("whatever").readlines()
results = []
for line in data:
if line.startswith("U(1.0"):
results.append(line)
Answer 3
Similar to manicphase's answer, use Python's startswith string method to pick out the lines you are interested in.
with open('mydata.txt') as data:
for line in data:
if line.startswith('U(1.0 '):
# Do stuff here
A little simpler than manicphase's solution and quicker, as you don't need to re-iterate over the list which, if you have a lot of data, might have an adverse effect.
I don't have enough reputation to comment on manicphase's answer, so I shall make a note here instead: The space delimiter after the 1.0 is important if the data can have more than one decimal point (question doesn't specify), otherwise it might match U(1.0234 xxxx) as well.
