问题与tight_layout在matplotlib渲染

Question

我有以下代码：

import matplotlib.pyplot as plt 
import matplotlib 
from matplotlib.ticker import AutoMinorLocator 
import matplotlib.ticker as ticker 
import pylab as pl 
import numpy as np 

matplotlib.rc('font',**{'family':'sans-serif','sans-serif':['Helvetica'], 'weight':'bold'}) 
from matplotlib.font_manager import fontManager, FontProperties 
matplotlib.rcParams['mathtext.fontset'] = 'custom' 
matplotlib.rcParams['mathtext.rm'] = 'Helvetica' 
matplotlib.rcParams['mathtext.it'] = 'Helvetica:italic' 
matplotlib.rcParams['mathtext.bf'] = 'Helvetica:bold' 
font= FontProperties(weight='bold',size=18) 

data = np.genfromtxt('data', names=True, dtype=None, usecols=("x", "y1", "y2", "y3")) 
x = data['x'] 
n = data['y1'] 
j = data['y2'] 
v = data['y3'] 
minorLocator = AutoMinorLocator(2) 
def format(): 
    for axis in ['top','bottom','left','right']: 
     ax.spines[axis].set_linewidth(3) 

    for tick in ax.yaxis.get_ticklabels(): 
      tick.set_fontsize(22) 
      tick.set_weight('bold') 

    for tick in ax.xaxis.get_ticklabels(): 
      tick.set_fontsize(22) 
      tick.set_weight('bold') 

    ax.set_ylabel(r'$\mathrm{ \Delta{}E_{solv}^{imp}}$',fontsize=26,fontweight='bold') 
    ax.tick_params(axis='x', which='both', direction='in', length=10, width=3, pad=8, top='off') 
    ax.tick_params(axis='y', which='major', direction='in', length=10, width=3, pad=8, right='off') 
    ax.tick_params(axis='y', which='minor', direction='in', length=6, width=2, right='off') 


fig = plt.figure(figsize=(9.6,12), dpi=300, linewidth=3.0) 
ax = fig.add_subplot(211) 

r=np.arange(1,25,1.5) 
p1 = ax.bar(r,v,width=0.9,color='white',edgecolor='black', lw=1.0, align='center') 
p2 = ax.bar(r,j,width=0.6,color='red',edgecolor='black', lw=1.0, align='center') 
p3 = ax.bar(r,n,width=0.3,color='black',edgecolor='black', lw=1.0, align='center') 

ax.set_xticks(r) 
ax.set_xticklabels(x,rotation=45) 
format() 
plt.axhline(y=0,linewidth=1,color='black') 
plt.axis([0.0,24.5,-0.36,0.15]) 
ax.yaxis.set_minor_locator(minorLocator) 
pl.rc('axes',linewidth=3) 
ax.xaxis.grid(True,which='major',color='gray', linestyle='--',linewidth=0.5) 
ax.set_axisbelow(True) 

data = np.genfromtxt('data-2', names=True, dtype=None, usecols=("x", "y1")) 
x = data['x'] 
n = data['y1'] 

ax = fig.add_subplot(212) 
r=np.arange(1,31,1.5) 
p1 = ax.bar(r,v,width=0.9,color='red',edgecolor='black', lw=1.0, align='center') 
ax.set_xticks(r) 
ax.set_xticklabels(x,rotation=90) 
format() 
plt.axhline(y=0,linewidth=1,color='black') 
plt.axis([0.0,30.5,-0.48,0.40]) 
for label in ax.xaxis.get_ticklabels():   
    label.set_horizontalalignment('center') 

ax.yaxis.set_minor_locator(minorLocator) 
pl.rc('axes',linewidth=3) 

ax.xaxis.grid(True,which='major',color='gray',linestyle='--',linewidth=0.5) 
ax.set_axisbelow(True) 
fig.set_tight_layout(True) #tried plt.tight_layout() also. didn't work 
plt.savefig('image.png',dpi=300,format='png', orientation='landscape') 

我不能救plt.show（）的图形。我收到以下错误。即使删除了fig.set_tight_layout（True）行，我仍然会收到同样的错误。发布这整个代码的原因是，如果我运行部分代码，我无法重现相同的错误。

谢谢你的帮助。

Traceback (most recent call last): 
    File "image.py", line 83, in <module> 
    plt.savefig('image.png',dpi=300,format='png', orientation='landscape') 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/pyplot.py", line 576, in savefig 
    res = fig.savefig(*args, **kwargs) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/figure.py", line 1470, in savefig 
    self.canvas.print_figure(*args, **kwargs) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/backend_bases.py", line 2192, in print_figure 
    **kwargs) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 513, in print_png 
    FigureCanvasAgg.draw(self) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 461, in draw 
    self.figure.draw(self.renderer) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/figure.py", line 1079, in draw 
    func(*args) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/axes/_base.py", line 2092, in draw 
    a.draw(renderer) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper 
    draw(artist, renderer, *args, **kwargs) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/axis.py", line 1105, in draw 
    renderer) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/axis.py", line 1054, in _get_tick_bboxes 
    extent = tick.label1.get_window_extent(renderer) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/text.py", line 741, in get_window_extent 
    bbox, info, descent = self._get_layout(self._renderer) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/text.py", line 320, in _get_layout 
    ismath=ismath) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 220, in get_text_width_height_descent 
    self.mathtext_parser.parse(s, self.dpi, prop) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/mathtext.py", line 3005, in parse 
    box = self._parser.parse(s, font_output, fontsize, dpi) 
    File "/usr/local/lib/python2.7/site-packages/matplotlib/mathtext.py", line 2339, in parse 
    six.text_type(err)])) 
ValueError: 
_ 
^ 
Expected "\" (at char 1), (line:1, col:2) 

Answer 1

这实际上是一些数学格式相关的问题，虽然不在ylabel中。我不知道为什么，但重新进入所有列表元素（包含几个$ A_a $）再次工作。