python-pygal画图

pygal是个非常简单且功能丰富的py画图包，折线图、柱状图、饼图等常见和不常见的图像都可轻松实现。

解决 中文字体问题、Linux系统乱码问题，输出PNG文件问题

安装：
pip install pygal
文档特别详细：
http://www.pygal.org/en/stable/documentation/index.html
如下为官网折线图实例：

line_chart = pygal.Line()
line_chart.title = 'Browser usage evolution (in %)'
line_chart.x_labels = map(str,range(2002,2013))
line_chart.add('Firefox',[None,None,16.6,25,31,36.4,45.5,46.3,42.8,37.1])
line_chart.add('Chrome',3.9,10.8,23.8,35.3])
line_chart.add('IE',[85.8,84.6,84.7,74.5,66,58.6,54.7,44.8,36.2,26.6,20.1])
line_chart.add('Others',[14.2,15.4,15.3,8.9,9,10.4,5.8,6.7,6.8,7.5])
chart.render()  # Return the svg as bytes

1. 设置x轴数据：line_chart.x_labels
2. y轴数据：line_chart.add
3. 绘图：line_chart.render()
4. 保存输出：
   bytes：chart.render() # Return the svg as bytes
   svg文件：chart.render_to_file(‘/tmp/chart.svg‘)
   png图片：chart.render_to_png(‘/tmp/chart.png‘)

pygal对输出图片,及中文不够友好，需要引入其他依赖包。
pip install webencodings
pip install tinycss2
pip install defusedxml
pip install cssselect2
pip install cairocffi
pip install CairoSVG

如果是linux环境安装cairo容易失败，可以下载对应的系统包进行安装：
https://launchpad.net/ubuntu/+source/pycairo/
我的ubuntu环境下载的：
python3-cairo_1.16.2-1_amd64.deb
安装：dpkg -i python3-cairo_1.16.2-1_amd64.deb

linux系统上输出 png会有乱码：
解决：windows的 C:WindowsFonts 下的微软雅黑.ttf文件copy到 linux的/usr/share/fonts目录

如下为我的一段代码，将字体改成微软，同时输出png：

#####################
# 折线图：
# 兼容linux 系统 png文字乱码：
#   windows C:WindowsFonts 下的微软雅黑.ttf文件copy到 linux/usr/share/fonts目录
#####################

import pygal
import cairo
from pygal.style import Style
from datetime import datetime
colors_dict = {
        1:'#009688',#
        2:'#F44336',#
        3:'#3F51B5',#
        }
def draw_line(data,x_label,y_title,title,colors_list):
    colors = []
    for idx in colors_list:
        if idx in colors_dict:
            colors.append(colors_dict[idx])
        else:
            colors.append(colors_dict[1])
    colors = tuple(colors)
    custom_style = Style(
      background='#FFFFFF',plot_background='#FFFFFF',value_background='rgba(229,229,1)',foreground='rgba(0,.87)',foreground_strong='rgba(0,foreground_subtle='rgba(0,.54)',# Monospaced font is highly encouraged
      font_family=(
      '"微软雅黑","华文细黑",Arial,Helvetica,sans-serif'),label_font_family=None,major_label_font_family=None,value_font_family=None,value_label_font_family=None,tooltip_font_family=None,title_font_family=None,legend_font_family=None,no_data_font_family=None,label_font_size=20,major_label_font_size=20,value_font_size=20,value_label_font_size=20,tooltip_font_size=14,title_font_size=30,legend_font_size=16,no_data_font_size=64,# Guide line dash array style
      guide_stroke_dasharray='6,1',major_guide_stroke_dasharray='6,opacity='.7',opacity_hover='.8',stroke_opacity='.8',stroke_opacity_hover='.9',transition='150ms',colors=colors,value_colors=(),ci_colors=())

    chart = pygal.Line(fill=True,style=custom_style,title=title,y_title=y_title,x_label_rotation=20,show_legend=False,width=1600,print_values=True,print_zeroes=False,print_values_position='top',show_minor_x_labels=False)
    chart.x_labels = x_label
    chart.x_labels_major = x_label[::5]
    for i in data:
        chart.add(i[0],i[1])
    return chart

if __name__=="__main__":
    data = [('IE',20.1])]
    x_label = ['2019-07-07','2019-07-08','2019-07-12','2019-07-14','2019-07-15','2019-07-16','2019-07-17','2019-07-18','2019-07-19','2019-07-20','2019-07-21']
    print(x_label)
    y_title = "嘿嘿嘿"
    title = "哈哈哈哈"
    save_path = 'test.png'
    chart = draw_line(data,[1])
    chart.render_to_png(save_path)