Python：列表长度为单个整数

Question

I'm new to Python and I'm trying to output the length of a list as a single integer, eg:

l1 = ['a', 'b', 'c'] 
len(l1) = 3

However, it is printing on cmdline with 1s down the page, eg: 1 1 1 1 1 1 etc

How can I get it to just output the number rather than a list of 1s?

(Here's the code:)

def Q3():
  from datetime import datetime, timedelta 
  inputauth = open("auth.log", "r") 
  authStrings = inputauth.readlines() 

  failedPass = 'Failed password for'
  for line in authStrings:
    time = line[7:15]
    dateHour = line[0:9]
    countAttack1 = []

    if time in line and failedPass in line:
      if dateHour == 'Feb  3 08':
        countAttack1.append(time)
        length1 = len(countAttack1)
        print(length1)

Ideally, I'd like it to output the number in a print so that I could format it, aka:

print("Attack 1: " + length1)

Answer 1

I think you are looping and ifs are inside a loop. If so, just print the length outside loop scope. Please share the complete code for a better answer

Answer 2

Well as Syed Abdul Wahab said, the problem is that the "list" is getting recreated each loop. This makes so that the print reports "1", as it is the actual length of the list. The other problem, repetition of the printng is similar - you are actually printing "each time in the loop".

The solution is then simple: you initialize the list outside the loop; and also report outside the loop.

def Q3():
  from datetime import datetime, timedelta 
  inputauth = open("auth.log", "r") 
  authStrings = inputauth.readlines() 

  failedPass = 'Failed password for'
  countAttack1 = []  # after this line the countAttack will be empty
  for line in authStrings:
    time = line[7:15]
    dateHour = line[0:9]

    if time in line and failedPass in line:
      if dateHour == 'Feb  3 08':
        countAttack1.append(time)

  length1 = len(countAttack1)
  print("Attack 1: " + str(length1))

I'd also like to take a bit of time to link you to string formatting While the documentation is complex it will make printing much easier, above print is trnasformed into:

print("Attack 1: {0}".format(length1))

---

Further analysing the code gives some peculiarities, you check if time is in the line string. - However just a few codelines above you create time from a slice of line - so it will always be inside line . (Except for the edge case where line is not of correct length, but that'll error anyways). So that if statement should be simplified to:

  if failedPass in line: 

Answer 3

Here is the function that prints the the length:

def print_length():
    if time in line and failedPass in line:    
        if dateHour == 'Feb  3 08':
           countAttack1.append(time)
    length1 = len(countAttack1)
    print(length1)
print_length()
>>>Print length of the List.