我如何只打印每 5 行

Question

我有一个包含以下内容的文本文件 ("name_data.txt")：

name: Kelo
family name: Lam
location: Asia
members: Kelo, Kiko, Jil

name: Miko
family name: Naiton
location: Japan
members: Miko,Kayati 

文本文件保持相同的模式（姓名、姓氏、位置、成员）

我想打印第一行，然后每隔 5 行打印一次，所以我只打印开头带有“名称”的行。 然后我想要一个名字列表

我希望我的输出是：

["Kelo","Miko"]

到目前为止，我得到了（虽然是错误的）：

name_data= load_local_file('name_data.txt',ignore_header=False,delimiter='\t')


def __init __(name_reader): 

    names=list()  
    count=0  
    name_line=5  
    line_number=0  

    for name in name_data:

        if line_number<5:  

            line_number +=1  

        if line_number ==5: 

            names.append(line_number)  

Answer 1

您可以通过将linenumber modulo 5 与数字进行比较来识别每五行。在您的情况下，这应该是0，因为您想要第一行和第 6 行、第 11 行，...（请注意，python 以索引 0 开头）

要获取行号以及内容，您可以使用enumerate 遍历文件。

然后要丢弃字符串的name: 部分并保留后面的内容，您可以使用str.split()。

一个有效的实现可能如下所示：

# Create an empty list for the names
names = []

# Opening the file with "with" makes sure it is automatically closed even
# if the program encounters an Exception.
with open('name_data.txt', 'r') as file:
    for lineno, line in enumerate(file):
        # The lineno modulo 5 is zero for the first line and every fifth line thereafter.
        if lineno % 5 == 0:
            # Make sure it really starts with "name"
            if not line.startswith('name'):
                raise ValueError('line did not start with "name".')
            # Split the line by the ":" and keep only what is coming after it.
            # Using `maxsplit=1` makes sure you don't run into trouble if the name 
            # contains ":" as well (may be unnecessary but better safe than sorry!)
            name = line.split(':', 1)[1]
            # Remove any remaining whitespaces around the name
            name = name.strip()
            # Save the name in the list of names
            names.append(name)

# print out the list of names
print(names)

您也可以使用带有 step 参数的 itertools.islice 来代替枚举：

from itertools import islice

with open('name_data.txt', 'r') as file:
    for line in islice(file, None, None, 5):
        ... # like above except for the "if lineno % 5 == 0:" line

---

根据您的需要，您可以考虑使用re 模块来完全解析文件：

import re
# The regular expression
group = re.compile(r"name: (.+)\nfamily name: (.+)\nlocation: (.+)\nmembers: (.+)\n", flags=re.MULTILINE)
with open(filename, 'r') as file:
    # Apply the regex to your file
    all_data = re.findall(group, file)
# To get the names you just need the first element in each group:
firstnames = [item[0] for item in all_data]

对于您的示例，firstnames 将是 ['Kelo', 'Miko']，如果您使用 [item[1] for item in all_data]，则类似，那么您将获得姓氏：['Lam', 'Naiton']。 要成功使用正则表达式，您必须确保它真正匹配您的文件布局，否则您会得到错误的结果。

Answer 2

你可以用列表理解在一行中做到这一点

c = open('test.txt', 'r').readlines()

# for every fifth line extract out name and store in list
a = [i.replace('name: ', '').replace('\n', '') for i in c[::5]]

print(a) # ['Kelo', 'Miko']

Answer 3

一个简单的方法如下：

with open('name_data.txt', 'r') as file:

    index = 0
    for line in file:
        if index % 5 == 0:
            print(line.split()[1])
        index += 1

Answer 4

假设name_data是文件中的行列表，你可以这样做

names = []
for i in range(1, len(name_data), 5):
    names.append(name_data[i].split(":")[1].strip())

Answer 5

有一个name_data.txt 文件，其数据如下： 1 2 3 4 5 6 7 8 9 10

以下是打印第一行和每 5 行的方法：

content = [line.rstrip('\n') for line in open('name_data.txt')]
names = []
limit = 4
fp = open("name_data.txt")
names.append(content[0])
for i, line in enumerate(fp):
    if i == limit:
        names.append(line)
        limit += 5
fp.close()
print(names)

结帐http://shortcode.pro/code/read-txt-file-and-print-first-and-every-5th-line/

Answer 6

您可以使用正则表达式 - Python 的模块是 re。

然后name_data.txt 是：

name: Kelo
family name: Lam
location: Asia
members: Kelo, Kiko, Jil

name: Miko
family name: Naiton
location: Japan
members: Miko,Kayati 

获取名称很简单：

import re

def get_names():

    with open('name_data.txt', 'r') as f:
        print(re.findall(r'^name:\s*(\w+)', f.read(), flags=re.MULTILINE))

if __name__ == '__main__':

    get_names()

注意多行标志设置 - 当设置为全局时，正则表达式也会匹配带有family name: ... 的行。 在交互模式下查看正则表达式here。