reportlab中Paragraph文字垂直居中

可以使用ReportLab中的`Paragraph`模块，结合`Table`模块来实现文字的垂直居中。

具体实现方法为：使用`valign`参数指定文字的垂直对齐方式，取值范围可以是`'top', 'middle', 'bottom'`。例如：

from reportlab.lib.pagesizes import letter
from reportlab.platypus import Paragraph, Table, TableStyle
from reportlab.lib import colors

data = [['Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam finibus nulla non urna pulvinar, ac luctus elit faucibus. Sed ex ipsum, imperdiet in aliquet ut, ultrices ut ex. Nunc tempus libero nec nisi rhoncus, at condimentum metus lobortis. Proin porta sodales orci, ut aliquet arcu luctus ut.',
         'Nam leo arcu, posuere ut purus rutrum, vulputate gravida nibh. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Donec posuere turpis eu urna accumsan egestas. Donec nisi mauris, commodo id mi vel, pretium scelerisque nibh.'],
        ['Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam finibus nulla non urna pulvinar, ac luctus elit faucibus. Sed ex ipsum, imperdiet in aliquet ut, ultrices ut ex. Nunc tempus libero nec nisi rhoncus, at condimentum metus lobortis. Proin porta sodales orci, ut aliquet arcu luctus ut.',
         'Nam leo arcu, posuere ut purus rutrum, vulputate gravida nibh. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Donec posuere turpis eu urna accumsan egestas. Donec nisi mauris, commodo id mi vel, pretium scelerisque nibh.']]

# 定义一个存放数据的Table实例
table = Table(data)

# 设置每个格子的样式
style = TableStyle([
    ('VALIGN', (0, 0), (-1, -1), 'MIDDLE'),
    ('ALIGN', (0, 0), (-1, -1), 'LEFT'),
    ('TEXTCOLOR', (0, 0), (-1, -1), colors.black),
    ('FONTNAME', (0, 0), (-1, -1), 'Helvetica'),
    ('FONTSIZE', (0, 0), (-1, -1), 10),
    ('BOTTOMPADDING', (0, 0), (-1, -1), 15),
])

table.setStyle(style)

# 将Table实例添加到Paragraph中
para = Paragraph(str(table), style)

# 保存到pdf文件
pdf_path = '/path/to/pdf'
c = canvas.Canvas(pdf_path, pagesize=letter)
para.wrapOn(c, 500, 500)
para.drawOn(c, 100, 500)
c.save()

上述代码中，使用`valign`参数将所有格子的文字垂直居中，文字水平靠左。然后将`Table`实例转换成`Paragraph`实例，并添加到canvas中即可。