Python：计数函数不起作用

Question

我被 Coursera Python 课程的练习困住了，这就是问题：

“打开文件 mbox-short.txt 并逐行读取它。当您找到以 'From ' 开头的行时，如下所示： 来自 [电子邮件受保护] 2008 年 1 月 5 日星期六 09:14:16 您将使用 split() 解析 From 行并打印出该行中的第二个单词（即发送消息的人的完整地址）。然后在最后打印出计数。 提示：确保不包含以“From:”开头的行。 您可以在http://www.pythonlearn.com/code/mbox-short.txt”

下载示例数据

这是我的代码：

fname = raw_input("Enter file name: ")
if len(fname) < 1 : fname = "mbox-short.txt"
fh = open(fname)
count = 0
for line in fh:
    words = line.split()
    if len(words) > 2 and words[0] == 'From':
        print words[1]
        count = count + 1
    else:
        continue        
print "There were", count, "lines in the file with From as the first word"`

输出应该是电子邮件列表及其总和，但它不起作用，我不知道为什么：实际上输出是“文件中有 0 行，以 From 作为第一个单词”

Answer 1

我使用了您的代码并从链接下载了文件。我得到这个输出：

文件中有 27 行，第一个单词为 From

您是否检查过您是否将文件下载到与代码文件相同的位置。

Answer 2

fname = input("Enter file name: ")
counter = 0
fh = open(fname)

for line in fh :
    line = line.rstrip()
    if not line.startswith('From '): continue        
    words = line.split()
    print (words[1])
    counter +=1

print ("There were", counter, "lines in the file with From as the first word")

Answer 3

fname = input("Enter file name: ")

fh = open(fname)
count = 0

for line in fh :

    if line.startswith('From '): # consider the lines which start from the word "From "

        y=line.split() # we split the line into words and store it in a list
        print(y[1])   # print the word present at index 1
        count=count+1  # increment the count variable

print("There were", count, "lines in the file with From as the first word")

我已经写了所有评论，如果有人遇到任何困难，如果您需要帮助，请随时与我联系。这是互联网上最简单的代码。希望我的回答对您有所帮助

Answer 4

fname = input('Enter the file name:')
fh = open(fname)
count = 0
for line in fh:
    if line.startswith('From'):
        linesplit =line.split()
        print(linesplit[1])
        count = count +1

Answer 5

fname = input("请输入文件名：") if len(fname) < 1 : fname = "mbox-short.txt"

fh = 打开（fname） 计数 = 0 对于我在fh：

i=i.rstrip()

if not i.startswith('From '): continue
word=i.split() 
count=count+1

print(word[1])

print("There were", count, "文件中以 From 作为第一个单词的行")

Answer 6

fname = input("Enter file name: ")
if len(fname) < 1 : fname = "mbox-short.txt"
fh = open(fname)
count = 0
for line in fh:
    if line.startswith('From'):  
        line=line.rstrip()
        lt=line.split()
        if len(lt)==2:
            print(lt[1])
            count=count+1
print("There were", count, "lines in the file with From as the first word")

Answer 7

我的代码看起来像这样并且具有魅力：

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

fh = open(fname)
count = 0 #initialize the counter to 0 for the start
for line in fh: #iterate the document line by line
    words = line.split() #split the lines in words
    if not len(words) < 2 and words[0] == "From": #check for lines starting with "From" and if the line is longer than 2 positions
        print(words[1]) #print the words on position 1 from the list
        count += 1 # count
    else:
        continue
print("There were", count, "lines in the file with From as the first word")

这是 Chuck 博士课程中的一个很好的练习

还有另一种方法。您可以将找到的单词存储在单独的空列表中，然后打印出列表的长度。它会产生相同的结果。

我测试的代码如下：

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

fh = open(fname)
newl = list()
for line in fh:
    words = line.split()
    if not len(words) < 2 and words[0] == 'From':
        newl.append(words[1])
    else:
        continue
print(*newl, sep = "\n")
print("There were", len(newl), "lines in the file with From as the first word")

我也用它通过了练习。享受并保持良好的工作。尽管我一直讨厌编程，但 Python 对我来说非常有趣。

Answer 8

file_name = input('Enter a file name: ')
count = 0
try:
    file_handle = open(file_name)
    for line in file_handle:
        words = line.rstrip().split()

         
        if len(words) == 0:
            continue

        if words[0] == 'From':
            count += 1
            print(words[1])

    print('There were', count, 'lines in the file with From as the first word')

except:
    print('Invalid File')