在 Python 中每个循环读取单行 CSV

Question

Python3.7 CSV

我已经重新构建了这个问题以使其更加明显 - 我试图在循环中的每次传递时从 CSV 访问特定行。

所以在第一个循环中取第 1 行

第二次循环出现在第 2 行

循环第三次出现，从 CSV 中取出第 3 行

test.csv：

How To Write Your First Article Heading,
Here's The Important Second Article Heading,
Three is The Magic Number,

脚本：

import csv

name = 'Article Heading'


for i in range(3):

    with open ('test.csv', 'r') as file:
        reader = csv.reader(file)
        for i in range(3):
            try:
                csv_row = ' '.join(next(reader))
            except StopIteration:
                break

            articletitle = (name + ' | ' + csv_row)
            print(articletitle)

print('THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV')

以上输出：

Article Heading | How To Write Your First Article Heading 
Article Heading | Here's The Important Second Article Heading 
Article Heading | Three is The Magic Number 
Article Heading | How To Write Your First Article Heading 
Article Heading | Here's The Important Second Article Heading 
Article Heading | Three is The Magic Number 
Article Heading | How To Write Your First Article Heading 
Article Heading | Here's The Important Second Article Heading 
Article Heading | Three is The Magic Number 
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV
[Finished in 0.3s]

期望的输出：

Article Heading | How To Write Your First Article Heading 
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV
Article Heading | Here's The Important Second Article Heading 
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV
Article Heading | Three is The Magic Number
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV

如果人们认为我把这完全搞砸了，我愿意接受严厉的批评。我保证我已经找到了解决方案，但没有快乐。

Answer 1

你遇到的问题是读取你使用list(csv.reader(infile))的csv文件

csv.reader(infile) 是一个迭代器，将在您的文件中逐行执行。

如果我正确理解了您的问题，您可以通过两种方式解决您的问题。

一个循环使用for _ in range(5) 循环 5 次：

with open ('test.csv', 'r') as file:
    reader = csv.reader(file)
    for i in range(5):
        try:
            csv_row = ' '.join(next(reader))
            print(csv_row)
        except StopIteration:
            break

（如果 csv 文件少于 5 行，您需要处理 StopIteration 异常）

或者您可以遍历 csv 文件的每一行并在循环的第 5 次迭代后中断：

with open ('test.csv', 'r') as file:
    reader = csv.reader(file)
    for i, line in enumerate(reader):
        if i == 5:
            break
        row = ' '.join(line)
        print(row)

在这个解决方案中，不需要处理任何异常，但是如果你想在第 5 次迭代后中断循环，你需要有一些 if 语句来查看当前正在进行的迭代。

Answer 2

遍历行很简单。在您的测试用例中，您甚至不需要 csv 模块，但我会使用您的测试用例：

代码：

import csv

name = 'Article Heading'

# newline='' should be used per documentation for csv.reader.
with open ('test.csv', newline='') as file:
    reader = csv.reader(file)
    for row in reader:
        articletitle = name + ' | ' + row[0]
        print(articletitle)
        print('THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV')

输出：

Article Heading | How To Write Your First Article Heading
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV
Article Heading | Here's The Important Second Article Heading
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV
Article Heading | Three is The Magic Number
THEN WE GO OFF AND DO SOMETHING BEFORE GOING BACK FOR THE NEXT ROW IN THE CSV

编辑

要遍历列，读取所有数据并将列转置为行：

test.csv：

1,4,7
2,5,8
3,6,9

代码：

import csv

name = 'Article Heading'

# newline='' should be used per documentation for csv.reader.
with open ('test.csv', newline='') as file:
    rows = list(csv.reader(file))

columns = zip(*rows) # transpose rows/columns

for column in columns:
    for item in column:
        article_title = f'{name} | {item}'
        print(article_title)

输出：

Article Heading | 1
Article Heading | 2
Article Heading | 3
Article Heading | 4
Article Heading | 5
Article Heading | 6
Article Heading | 7
Article Heading | 8
Article Heading | 9