Matplotlib水平地剪切hbar中的第一个条形

Question

我正在努力理解为什么matplotlib hbar图中的第一个横条正在水平切成两半。该栏上也缺少yaxis标签。知道为什么会这样吗？

这是脚本，附件是输出

import networkx as nx
import matplotlib.pyplot as plt
from matplotlib import cm
import numpy as np
import neptcon as nc
import sys
import pickle

fp = open("C:\Python27\Internal_reports\\shared.pkl")
shared = pickle.load(fp)

con = None

cur, con = nc.connect()
cur = con.cursor()   
scriptFile = open("C:\Python27\Internal_reports\Ann_report_sql\Den diff.sql", 'r')
script = scriptFile.read()
scriptFile.close()    
cur.execute(script.format(**shared))
items = cur.fetchall()
client, ship, imo, diff = zip(*items)
new_list = []
for item in diff:
    new_list.append(int(item))          
N = len( new_list )
x = range( N )   
n_groups = N
index = np.arange(n_groups)
fig = plt.figure()
f, (ax1) = plt.subplots(1, 1, figsize=(8, N/2), sharex=False)
bar_width = 0.95
opacity = 0.5
G = nx.complete_graph(10)
pos = nx.spring_layout(G)

plt.yticks(index+(bar_width/2), ship, fontsize = 9)
ax1.yaxis.grid(True, which='major', color='0.95',linestyle='-')
ax1.set_ylim(0, N)
ax1.xaxis.set_ticks_position('bottom')
ax1.yaxis.set_ticks_position('right')
ax1.spines['right'].set_visible(False)
ax1.spines['top'].set_visible(False)
ax1.spines['left'].set_visible(False)
for a,b in zip(index,new_list):
    plt.text(b, a-0.2, str(b))  
    plt.barh(a,b,color=cm.autumn(1.*a/len(x)),edgecolor='white')
if N > 40:
    plt.savefig('{} quan_diff.pdf'.format(shared.get("cl")), format='pdf', bbox_inches='tight')
else:
    plt.savefig('C:\Python27\Internal_reports\plots\\quan_diff.png', bbox_inches='tight')

nc.closeCon()