How to extract hour from the time

user_13848940 0
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I have a text file (in an email format) that I need to extract out the hours (in HH:MM:SS format). I initially split the text but can't seem to split the results again to grab the time only. If I do manage to isolate the time and try again, it provides me with

AttributeError: 'list' object has no attribute 'split'"

Text Sample

From stephen.marquard@uct.ac.za Sat Jan  5 09:14:16 2008

Here is my code

name = input('Enter File:')
input to default to mbox-short.txt
if len(name) < 1 : name = 'mbox-short.txt'
handle = open(name)

counts = dict()
for line in handle:
    line = line.rstrip()
    if line.startswith('From '):
        words = line.split()
        time = words[5:6]
        print(time)
        hour = time.split(':')
        print(hour)

The eventual goal is to build a histogram/time-series - any insights would be helpful to get past this part so I can continue!

python split
4 Answers

When you do this:

time = words[5:6]

You are going to get a list back. Any time you get a "slice" of a list like this, it returns another list. So time is a list. You could "unpack" the list (which will always have just one element) like this:

[time] = words[5:6]

and then your code will work.

user_137384640

You are slicing a sequence (words[5:6]) and it will give you a sub-sequence, i.e. a shorter sequence of the same type as the original one. What you need to do get the element at position 5 is to use indexing notation: words[5] -- this will give you the element at that position alone.

user_79181730

It's because the result of string.split() is list. You need to pull the string that you want out of the list and then split that.

handle=['From stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008']
for line in handle:
    line = line.rstrip()
    if line.startswith('From '):
        words = line.split()
        
        # time = words[5:6]
        # time=time[0] # extract the string

        # this is better than extracting yet another sub list though
        time = words[5]

        print(time)
        hour = time.split(':')
        print(hour)

output:

09:14:16
['09', '14', '16']
user_24643810

May I introduce you to Regular Expressions, or regex. This is a very useful sub-language used for text pattern matching - perfect for your hour extraction example.

Here is a link to an excellent online tool for testing/learning patterns.

For example:

Text string: From stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008

From your text string above you can write the pattern: (\d{2}):\d{2}:\d{2} to extract the hours. With the output being: 09.

Breakdown:

  • The () creates a 'capture group'; the set of values you want to extract.
  • \d matches any character which is a digit
  • {2} matches 2 of the previous tokens, in this case, a digit
  • : matches the literal ':' character

String it all together and you can match the time pattern of (2digits):2digits:2digits with the first set of 2digits being extracted.

In Python:

import re

text = 'From stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008'
exp = r'(\d{2}):\d{2}:\d{2}'

# Search for the pattern in the text string.
m = re.search(exp, text)
# Extract and print the first match (0 index) from the matches found.
print(m.groups()[0])

Output:

09

user_63404960
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