python - 如何在Python中的前两个打印行之间添加一行破折号？

Question

我正在尝试从 csv 文件在控制台中创建一个表。为了使输出看起来更像表格，我想在第二行添加一行破折号来分割标题和主表格内容。

这是我到目前为止的代码:

import csv

with open('filename.csv', mode='r') as csv_file:
    csv_reader = csv.reader(csv_file)
    line_count = 0
    for row in csv_reader:
        if line_count == 0:
            print("|",row[0]," "*(20-len(row[0])), "|",
              row[1], " " * (15 - len(row[1])), "|",
              row[2], " " * (20 - len(row[2])), "|",
              row[3], " " * (5 - len(row[3])), "|")

这是输出:

| Track           | Artist           | Album                 | Time   |
| Songname 1      | Artist 1         | Album 1               | 7:15   |
| Songname 1      | Artist 2         | Album 2               | 6:27   |
| Songname 1      | Artist 3         | Album 3               | 5:24   |
| Songname 1      | Artist 4         | Album 4               | 2:50   |
| Songname 1      | Artist 5         | Album 5               | 4:39   |
| Songname 1      | Artist 6         | Album 6               | 5:11   |
| Songname 1      | Artist 7         | Album 7               | 2:56   |
| Songname 1      | Artist 8         | Album 8               | 4:29   |
| Songname 1      | Artist 9         | Album 9               | 3:17   |
| Songname 1      | Artist 10        | Album 10              | 3:04   |

Process finished with exit code 0

这是我想要实现的输出:

-----------------------------------------------------------------------
| Track           | Artist           | Album                 | Time   |
-----------------------------------------------------------------------
| Songname 1      | Artist 1         | Album 1               | 7:15   |
| Songname 1      | Artist 2         | Album 2               | 6:27   |
| Songname 1      | Artist 3         | Album 3               | 5:24   |
| Songname 1      | Artist 4         | Album 4               | 2:50   |
| Songname 1      | Artist 5         | Album 5               | 4:39   |
| Songname 1      | Artist 6         | Album 6               | 5:11   |
| Songname 1      | Artist 7         | Album 7               | 2:56   |
| Songname 1      | Artist 8         | Album 8               | 4:29   |
| Songname 1      | Artist 9         | Album 9               | 3:17   |
| Songname 1      | Artist 10        | Album 10              | 3:04   |
-----------------------------------------------------------------------

Answer 1

您可以使用 string format mini language 让您的代码变得更加简单:

t = """Track,Artist,Album,Time
Songname 1,Artist 1,Album 1,7:15
Songname 1,Artist 2,Album 2,6:27
"""
with open("t.txt","w") as w:
    w.write(t)


import csv

with open('t.txt', mode='r') as csv_file:
    csv_reader = csv.reader(csv_file)
    for idx, row in enumerate(csv_reader):
        if idx == 0:
            print("-"*65)

        # string format mini language:
        #  {:<20} means take the n-th provided value and right align in 20 spaces
        print("|{:<20}|{:<15}|{:<20}|{:<5}|".format(*row))  # *row == row element wise
        if idx == 0:
            print("-"*65)
    print("-"*65)

输出:

-----------------------------------------------------------------
|Track               |Artist         |Album               |Time |
-----------------------------------------------------------------
|Songname 1          |Artist 1       |Album 1             |7:15 |
|Songname 1          |Artist 2       |Album 2             |6:27 |
-----------------------------------------------------------------

<小时/>

如果您想省略行时间并使用自适应宽度而无需硬编码长度，则标题提取的替代解决方案:

演示文件:

t = """Track,Artist,Album,Time
Very Long Songname 1,Artist 1,Album 1,7:15
Songname 1,Artist 2,Album 2 title with epic proportions,6:27
"""
with open("t.txt","w") as w:
    w.write(t)

代码:

import csv

def get_format_string(w):
    s = '|'+'|'.join(" {{:<{}}} ".format(l) for _,l in sorted(w.items()))+'|'
    return s.format

def get_widths(reader,filehandle):
    """Calculate maximum widths of columns. Rewinds filehandle to seek(0)."""
    widths = {}
    for row in reader:
        for i,c in enumerate(row):
            widths[i] = max(widths.get(i,0), len(c))
    # rewind
    filehandle.seek(0)
    return widths  

with open('t.txt', mode='r') as csv_file:
    csv_reader = csv.reader(csv_file)
    fmt = get_format_string(get_widths(csv_reader,csv_file))

    header = fmt(*(next(csv_reader)))
    w = len(header)
    print("-"*w)
    print(header)
    print("-"*w)

    # deal with the rest of the data
    for row in csv_reader:
        print(fmt(*row))

    # and the last line
    print("-"*w)

输出:

--------------------------------------------------------------------------------
| Track                | Artist   | Album                               | Time |
--------------------------------------------------------------------------------
| Very Long Songname 1 | Artist 1 | Album 1                             | 7:15 |
| Songname 1           | Artist 2 | Album 2 title with epic proportions | 6:27 |
--------------------------------------------------------------------------------