python - 如何计算python文本文件中相同关键字出现两次的行数？

Question

我有一个 python scraping 脚本来获取一些即将到来的音乐会的信息，并且无论有多少音乐会出现，每次都是相同的文本模式，唯一的区别是有时它会显示一个额外的行仍然可以预订时的门票价格，例如以下示例：

LIVE 01/01/99 9PM
Iron Maiden
Madison Square Garden 
New York City
LIVE 01/01/99 9.30PM
The Doors
Staples Center
Los Angeles
LIVE 01/02/99 8.45PM
Dr Dre & Snoop Dogg
Staples Center
Los Angeles
Book a ticket now for $99,99
LIVE 01/02/99 9PM
Diana Ross
City Hall
New York City 
Book a ticket now for $79,99       ect...

我需要计算每个文本块的行数并检查它是 4 行还是 5 行，所以我想的是计算每个块的第一个单词的出现（“LIVE”）和然后添加一个 if 语句来对 2 个类别（4 行块和 5 行块）之间的块进行排序

if 语句部分并不难，但我只是不知道如何做第一部分，也许是 readlines 然后当一行有关键字“LIVE”时，添加行位置（提供数据样本分别是第1行、第5行、第9行、第14行，这里我们可以清楚地看到前2个块是4行，而第3个是5行）然后if语句部分将它们整理出来

任何帮助将不胜感激，谢谢！

用我的代码想法编辑，我希望它会更清楚，我需要获取变量 line_number 和 gap_each_line 的代码：

with open('concerts_list.txt', 'r') as file:          
    reading_file = file.read()
    lines = reading_file.split('\n')
    for "LIVE" in lines:
        line_number = #the part where I'm stuck to tell each line number
 where the word "LIVE" appears. output desired: [0, 4, 8, 13]
        gap_each_line = #calculate the gap between each number of previous 
variable line_number. output desired: [4, 4, 5]
    if gap == 4 for gap in gap_each_line:
        dates = [i for i in lines [0::4]]
    elif gap == 5 for gap in gap_each_line:
        dates = [i for i in lines [0::5]]

Answer 1

您可以使用read_csv of pandas 模块。

我希望您的整个问题（查找日期等）都可以使用pandas 解决。

下面是查找以'LIVE'开头的行之间的行差异的代码

import pandas as pd
df = pd.read_csv('/Users/prince/Downloads/test3.csv', sep='~~~', header=None, engine='python')
df.columns = ['Details']
df['si_no'] = df['Details'].str.startswith('LIVE').cumsum()
gaps = df.groupby('si_no').apply(lambda x : len(x)).values
print(gaps)

它会打印出来

[4 4 5 5]

Answer 2

我知道您提供了您想要的输出（弗朗西斯王子的回答），但我感觉您正在尝试以困难的方式解决问题。

请看这个：

from collections import defaultdict #Defaultdict let's you create a dictionary, which is already set up to contain a list for every key

concerts = defaultdict(list)
current_dictKey = None # Starts "unset"
with open('/tmp/concerts_list.txt', 'r') as file:
    reading_file = file.read()
    lines = reading_file.split('\n')
    for line in lines:
        print('I just read the following:', line)
        if line.startswith('LIVE'):
            print('The current line starts with keyword "live", so this will be the dictionarys new Key')
            current_dictKey = line
            continue # Continue to next line without doing anything else

        if line.startswith('Book a ticket'):
            print("This line starts with 'book a ticket'. Let's skip those too.")
            continue # Skip those lines. I guess you don't want them either.

        concerts[current_dictKey].append(line) # Just add the line to the Key in defaultdict


print()
print('This is the object "concerts"you get as the result:')
print(concerts)
print()


print('You can access a specific value like this:', concerts['LIVE 01/01/99 9PM'])

一旦它在字典中，您就可以非常轻松地访问所有数据。

Answer 3

（我创建了一个新答案，因为我仍然认为我的第一个答案更适合大多数情况。）

这将创建您想要的输出：

live_lines = []
line_counter = 0
distances = []
with open('concerts_list.txt', 'r') as file:
    reading_file = file.read()
    lines = reading_file.split('\n')
    for line in lines:
        if line.startswith('LIVE'):
            live_lines.append(line_counter)

        line_counter += 1

for position in range(len(live_lines)-1):
    new_distance = live_lines[position+1] - live_lines[position]
    distances.append(new_distance)

print('live_lines:', live_lines)
print('distances', distances)

输出：

live_lines: [0, 4, 8, 13]
Distances [4, 4, 5]

Answer 4

与你写的类似，但写的更pythonic。

with open('concerts_list.txt', 'rt') as file:
    indices = [index for index, line in enumerate(file) if line.startswith("LIVE")]
    block_lengths = [adjacent - current for current, adjacent in zip(indices , indices [1:])]

如果您的文件非常大，您可以使用generator comprehension、itertools.tee、itertools.islice 来延迟加载您需要在内存中进行计算的数据。因此，与这里的第一个示例相比，您使用 Iterator 对象而不是内存列表来处理数据流。

import itertools

with open('concerts_list.txt', 'rt') as file:
    # generator comprehension
    indices = (index for index, line in enumerate(file) if line.startswith("LIVE"))
    # itertools.tee make copies of iterators
    indices_1, indices_2 = itertools.tee(indices)
    # here itertools.islice make new iterator without first element
    block_lengths = [adjacent - current for current, adjacent in
                     zip(indices_1, itertools.islice(indices_2, 1, None))]