如何优化我的代码？ （建议）

Question

Im new to Python and im taking an online course. One of the problems i have to solve is this:

10.2 Write a program to read through the mbox-short.txt and figure out the distribution by hour of the day for each of the messages. You can pull the hour out from the 'From ' line by finding the time and then splitting the string a second time using a colon.

From xyz.abc@ab.cd.de Sat Jan 5 09:14:16 2008

Once you have accumulated the counts for each hour, print out the counts, sorted by hour as shown below.

My code is this:

name = input("Enter file:")
if len(name) < 1 : name = "mbox-short.txt"
handle = open(name)
lst= []
lst2=[]
lst3=[]
ddd= {}

for l in handle:
    if l.startswith("From"):
        y= l.split()
        leg= len(y)
        if leg > 2:
            x= y[5]
            lst.append(x)


for h in lst:
    y= h.split(":")
    x= y[0]
    lst2.append(x)

for v in lst2:
    ddd[v]= ddd.get(v,0) + 1

for k, v in ddd.items():
    tup = (k, v)
    lst3.append (tup)

lst3= sorted(lst3)

for k, v in lst3:
    print (k, v)

giving this output:

04 3
06 1
07 1
09 2
10 3
11 6
14 1
15 2
16 4
17 2
18 1
19 1

Which is actually the correct answer. However im sure this code looks horrible for most people. Do you have any suggestions for me or my future coding? I want to be able to optimize my codes and not just write whatever come to my mind. Sorry if my english is bad.

Answer 1

Checkout Python PEP 8 for style suggestions.

Some suggestions (others may disagree)

1. If conditional on same line (sometimes okay but discouraged for long lines)

Change:

if len(name) < 1 : name = "mbox-short.txt"

To:

if len(name) < 1 : 
  name = "mbox-short.txt"

2. Initialize variables near their first usage.

So remove these initializations at the top since they provide no context.

lst= []
lst2=[]
lst3=[]
ddd= {}

3. Code is harder to follow with lots of non-descript variable names.

Posted code (too many non-descript variables):

for l in handle:
    if l.startswith("From"):
        y= l.split()
        leg= len(y)
        if leg > 2:
            x= y[5]
            lst.append(x)

Change to:

times = []
for line in handle:
    if line.startswith("From"):
      fields = line.split()
      if len(fields) > 5:
        times.append(fields[5])

Posted code (too many non-descript variables):

for h in lst:
  y= h.split(":")
  x= y[0]
  lst2.append(x)

Change To:

hours = []
for h in times:
  hours.append(h.split(":")[0])

Or even better (use list comprehension):

hours = [h.split(":")[0] for h in times]

Refactored Code

name = input("Enter file:")
if len(name) < 1 : 
  name = "mbox-short.txt"

with open(name) as handle:             # with is preferred over plain open
  times = []
  for line in handle:
      if line.startswith("From"):
        fields = line.rstrip().split() # strip to get rid of '\n'
        if len(fields) > 5:
          times.append(fields[5])

hours = [h.split(":")[0] for h in times]  # list comprehension

counts = {}
for v in hours:
    counts[v]= counts.get(v,0) + 1

counts = sorted(counts.items())              # create tuples and sort

for k, v in counts:
    print (k, v)