检查列表中字符串的最后一个元素

Question

I have got some serial communications logs to analyze regarding time, so I record messages with timestamps in format YYYY-MM-DD HH:MM:SS.ffffff: So my file looks like this:

YYYY-MM-DD HH:MM:SS.ffffff:

few lines of bytes

YYYY-MM-DD HH:MM:SS.ffffff:

and so on...

I want to extract dates from my file so I could calculate times between messages

I want to operate on dates using datetime module, and for the beginning I wanted to get rid of the colons at the end of each date. I have read my file and saved it in variable which is a list of strings, and each element is a line. Now I want to create a second list of only dates, extracting only those lines that end with colons.

f=open("sniffinglog.txt","r")

lines=(f.readlines())
lines_number=len(lines)
i=0
dates=[]
while i<lines_number:
    if lines[i].endswith(":"):
        dates.append(lines[i])
    i+=1 
print (dates)

I checked that lines is created correctly, however there are no elements appended to the list dates . It remains empty. Is there something wrong with my if condition? Or is there another way of checking last character of a string if it is a list element?

Answer 1

This should work, if it doesn't then your lines probably don't end with : .

with open("sniffinglog.txt", "r") as f:
    content = f.readlines()

dates = []
for line in content:
    if line.strip().endswith(":"):
        dates.append(line.rstrip(":"))

print(dates)

Answer 2

You need to remove the new line from every line of the file.

Try to replace

lines=(f.readlines())

with

lines=[l.strip() for l in f.readlines()]

Answer 3

A better way to find the Timestamp in line

f=open("sniffinglog.txt","r")

lines=(f.readlines())
lines_number=len(lines)
i=0
dates=[]
while i<lines_number:
    # Check if line is a timestamp.
    if time.strptime(line[:19], '%Y-%m-%d %H:%M:%S'):
        dates.append(lines[i])
    i+=1 
print (dates)