Tkinter中如何实现多个不同列数的Treeview控件左对齐

问题背景 #

开发目标为基于列数互不相同的多个DataFrame创建对应Treeview控件，每个Treeview放置在独立Frame中，所有子Frame统一收纳在主Frame内。现有代码已完成绝大多数功能，仅列数较少的小规模DataFrame对应的Treeview无法靠左对齐，呈现居中显示效果；尝试调整pack方法的side参数为left、top、bottom等取值，均未实现所有Treeview左对齐的效果。
原有实现代码如下：

import numpy as np
import pandas as pd
import string
import tkinter as tk
from tkinter import ttk
string.ascii_lowercase
n = 5
m = 25
cols11 = string.ascii_lowercase[:m]
df = pd.DataFrame(np.random.randint(0, n,size=(n , m)), columns=list(cols11))
a = 5
b = 15
cols12 = string.ascii_lowercase[:b]
df1 = pd.DataFrame(np.random.randint(0, a,size=(a , b)), columns=list(cols12))
c = 5
d= 10
cols22 = string.ascii_lowercase[:d]
df2 = pd.DataFrame(np.random.randint(0, c,size=(c , d)), columns=list(cols22))
e = 5
f= 5
cols32 = string.ascii_lowercase[:f]
df3= pd.DataFrame(np.random.randint(0, e,size=(e , f)), columns=list(cols32))
cols = list(df.columns)
cols1 = list(df1.columns)
cols2 = list(df2.columns)
cols3 = list(df3.columns)

root1 = tk.Tk()
main_frame=tk.Frame(root1)
main_frame.pack(fill=tk.BOTH,expand=1)
my_canvas=tk.Canvas(main_frame)
my_canvas.pack(side=tk.LEFT,fill=tk.BOTH,expand=1)
my_scrollbary=tk.Scrollbar(main_frame,orient=tk.VERTICAL,command=my_canvas.yview)
my_scrollbary.pack(side=tk.RIGHT,fill=tk.Y)
my_scrollbarx=tk.Scrollbar(root1,orient=tk.HORIZONTAL,command=my_canvas.xview)
my_scrollbarx.pack(side=tk.BOTTOM,fill=tk.X)
my_canvas.configure(yscrollcommand=my_scrollbary.set, xscrollcommand=my_scrollbarx.set)
my_canvas.bind('<Configure>', lambda e:my_canvas.configure(scrollregion=my_canvas.bbox("all")))
root=tk.Frame(my_canvas)
my_canvas.create_window((0,0),window=root,anchor="nw")
frame1=tk.Frame(root)
frame1.pack(anchor='w')
tree = ttk.Treeview(frame1)
tree.pack()
tree["columns"] = cols
for i in cols:
    tree.column(i, anchor="w")
    tree.heading(i, text=i, anchor='w')
for index, row in df.iterrows():
    tree.insert("",0,text=index,values=list(row))

frame2=tk.Frame(root)
frame2.pack(anchor='w')
tree1 = ttk.Treeview(frame2)
tree1.pack()
tree1["columns"] = cols1
for i in cols1:
    tree1.column(i, anchor="w")
    tree1.heading(i, text=i, anchor='w')
for index, row in df1.iterrows():
    tree1.insert("",0,text=index,values=list(row))

frame3=tk.Frame(root)
frame3.pack(anchor='w')
tree2 = ttk.Treeview(frame3)
tree2.pack()
tree2["columns"] = cols2
for i in cols2:
    tree2.column(i, anchor="w")
    tree2.heading(i, text=i, anchor='w')
for index, row in df2.iterrows():
    tree2.insert("",0,text=index,values=list(row))
#
frame4=tk.Frame(root)
frame4.pack(anchor='w')
tree3 = ttk.Treeview(frame4)
tree3.pack()
tree3["columns"] = cols3
for i in cols3:
    tree3.column(i, anchor="w")
    tree3.heading(i, text=i, anchor='w')
for index, row in df3.iterrows():
    tree3.insert("",0,text=index,values=list(row))
root.mainloop()

问题原因 #

代码中仅给承载Treeview的子Frame设置了anchor='w'实现Frame本身在父容器内左对齐，但Treeview控件在所属子Frame内调用pack()时未指定对齐参数，默认居中对齐；由于子Frame宽度会匹配最宽的Treeview宽度，列数更少、宽度更窄的Treeview就会在Frame内居中显示，视觉上呈现没有靠左对齐的效果。

修复方法 #

将所有Treeview的pack调用补充anchor='w'参数，强制Treeview在所属父Frame内靠左停靠，需要修改的4处代码如下：

• 原tree.pack()修改为tree.pack(anchor='w')
• 原tree1.pack()修改为tree1.pack(anchor='w')
• 原tree2.pack()修改为tree2.pack(anchor='w')
• 原tree3.pack()修改为tree3.pack(anchor='w')

修改后所有Treeview均可正常实现左对齐效果。

内容的提问来源于stack exchange，提问作者Orlando