Python在文件中找到最后一次出现

Question

I have a file with different IP's.

192.168.11.2
192.1268.11.3
192.168.11.3
192.168.11.3
192.168.11.2
192.168.11.5

This is my code until now. Where I print the IP and the occurence, but how can I found out when the last occurennce was for each of the IP's. Is it a simple way to do so?

liste = []

dit = {}
file = open('ip.txt','r')

file = file.readlines()

for line in file:
        liste.append(line.strip())

for element in liste:
        if element in dit:
                dit[element] +=1
        else:
                dit[element] = 1

for key,value in dit.items():
        print "%s occurs %s times, last occurence at line"  %(key,value)

Output:

192.1268.11.3 occurs 1 times, last occurence at line
192.168.11.3 occurs 2 times, last occurence at line
192.168.11.2 occurs 2 times, last occurence at line
192.168.11.5 occurs 1 times, last occurence at line

Answer 1

Try this:

liste = []

dit = {}
file = open('ip.txt','r')

file = file.readlines()

for line in file:
        liste.append(line.strip())

for i, element in enumerate(liste, 1):
        if element in dit:
                dit[element][0] += 1
                dit[element][1] =  i
        else:
                dit[element] = [1,i]

for key,value in dit.items():
        print "%s occurs %d times, last occurence at line %d" % (key, value[0], value[1])

Answer 2

Here is a solution:

from collections import Counter

with open('ip.txt') as input_file:
    lines = input_file.read().splitlines()

    # Find last occurrence, count
    last_line = dict((ip, line_number) for line_number, ip in enumerate(lines, 1))
    ip_count = Counter(lines)

    # Print the stat, sorted by last occurrence
    for ip in sorted(last_line, key=lambda k: last_line[k]):
        print '{} occurs {} times, last occurence at line {}'.format(
            ip, ip_count[ip], last_line[ip])            

Discussion

• I use the enumerate function to generate line number (starting at line 1)
• With a sequence of (ip, line_number), it's easy to generate the dictionary last_line where the key is the IP address and the value is the last line it occurs
• To count the number of occurences, I use the Counter class--very simple
• If you want the report sorted by IP address, use sorted(last_line)
• This solution has a performance implication: it scans the list of IPs twice: once to calculate last_line and once to calculate ip_count . That means this solution might not be ideal if the file is large

Answer 3

last_line_occurrence = {}
for element, line_number in zip(liste, range(1, len(liste)+1)):
     if element in dit:
            dit[element] +=1
     else:
            dit[element] = 1
     last_line_occurrence[element] = line_number

for key,value in dit.items():
     print "%s occurs %s times, last occurence at line %s"  %(key,value, last_line_occurrence[key])

Answer 4

This can easily be done in a single pass without reading all the file into memory:

from collections import defaultdict
d = defaultdict(lambda: {"ind":0,"count":0})

with open("in.txt") as f:
    for ind, line in enumerate(f,1):
        ip = line.rstrip()
        d[ip]["ind"] = ind
        d[ip]["count"]  += 1

for ip ,v in d.items():
    print("IP {}  appears {} time(s) and the last occurrence is at  line {}".format(ip,v["count"],v["ind"]))

Output:

IP 192.1268.11.3  appears 1 time(s) and the last occurrence is at line 2
IP 192.168.11.3  appears 2 time(s) and the last occurrence is at line 4
IP 192.168.11.2  appears 2 time(s) and the last occurrence is at line 5
IP 192.168.11.5  appears 1 time(s) and the last occurrence is at line 6

If you want the order the ip's are first encountered use an OrderedDict:

from collections import OrderedDict
od = OrderedDict()
with open("in.txt") as f:
    for ind, line in enumerate(f,1):
        ip = line.rstrip()
        od.setdefault(ip, {"ind": 0,"count":0})
        od[ip]["ind"] = ind
        od[ip]["count"] += 1

for ip ,v in od.items():
    print("IP {}  appears {} time(s) and the last occurrence is at  line {}".format(ip,v["count"],v["ind"]))

Output:

IP 192.168.11.2  appears 2 time(s) and the last occurrence is at line 5
IP 192.1268.11.3  appears 1 time(s) and the last occurrence is at line 2
IP 192.168.11.3  appears 2 time(s) and the last occurrence is at line 4
IP 192.168.11.5  appears 1 time(s) and the last occurrence is at line 6

Answer 5

You can use another dictionary. In this dictionary you store, for each line, the line number of the last occurrence and overwrite every time you find another occurrence. At the end, in this dictionary you will have, for each line, the line number of the last occurrence.

Obviously you will need to increment a counter for each read line in order to know the line you're reading right now.