title: openpyxl KeyError Worksheet {0} does not exist
body: <p>I know you probably have seen this title, but please dont mark as duplicate as my error is different. I am making an excel comparing program with openpyxl and using tkinter to make the UI more friendly. Here is my code:</p>
  
  <pre><code>import openpyxl
  from tkinter import *
  from tkinter.filedialog import askopenfilename
  from openpyxl.utils import get_column_letter, column_index_from_string
  
  f1 = ''
  f2 = ''
  sheet1 = ''
  sheet2 = ''
  
  root = Tk()
  root.configure(background='light green')
  root.geometry("500x500")
  root.wm_title("BananaCell")
  
  e1 = Text(root, width=15, height=1)
  e1.pack()
  e1.place(x=70, y=150)
  
  
  e2 = Text(root, width=15, height=1)
  e2.pack()
  e2.place(x=300, y=150)
  
  def destroy():
      root.destroy()
  
  def get_1():
      inputValue = e1.get("1.0", "end-1c")
      print(inputValue)
  
  def get_2():
      inputValue2 = e2.get("1.0", "end-1c")
      print(inputValue2)
  
  bf = Button(root, text="Enter", width=6, height=0, command=get_1)
  bf.pack()
  bf.place(x=15, y=147)
  
  bf = Button(root, text="Enter", width=6, height=0, command=get_2)
  bf.pack()
  bf.place(x=430, y=147)
  
  def askForFileName1():
      global f1
      f1 = askopenfilename(title="Select Workbook 1")
      print(str(f1))
  
  
  def askForFileName2():
      global f2
      f2 = askopenfilename(title="Select Workbook 2")
      print(str(f2))
  
  sheet1 = e1.get("1.0", "end-1c")
  sheet2 = e2.get("1.0", "end-1c")
  
  b = Button(root, text="Workbook 1", width=12, height=2, command=askForFileName1)
  b.pack()
  b.place(x=100, y=100)
  
  b2 = Button(root, text="Workbook 2", width=12, height=2, command=askForFileName2)
  b2.pack()
  b2.place(x=300, y=100)
  
  mainloop()
  
  wb = openpyxl.load_workbook(str(f1))
  wb1 = openpyxl.load_workbook(str(f2))
  
  ws = wb.get_sheet_by_name(str(sheet1))
  ws1 = wb1.get_sheet_by_name(str(sheet2))
  
  col1 = input('Column letter from Sheet 1 to compare from: ')
  col2 = input('Column letter  from Sheet 2 to compare from: ')
  
  for (col, col_1) in zip(ws.iter_cols(min_col = column_index_from_string(col1), max_col=column_index_from_string(col1)), ws1.iter_cols(min_col = column_index_from_string(col2), max_col=column_index_from_string(col2))):
      for (cell, cell_1) in zip(col, col_1):
         if cell.value != cell_1.value and cell.row == cell_1.row:
             print('Row ' + str(cell.row) + ' ' + str(cell.value) + ' is not 
  equal to ' + str(cell_1.value) + ' ' + 'Row ' + str(cell_1.row))
  
  exit_if = input('Press x to exit when you\'re ready: ')
  </code></pre>
  
  <p>Everything runs fine until I get to the line with: <code>ws = wb.get_sheet_by_name(str(sheet1))</code>. After that line it gives me the error:</p>
  
  <pre><code>raise KeyError("Worksheet {0} does not exist.".format(key))
  KeyError: 'Worksheet  does not exist.'
  </code></pre>
  
  <p>Can anyone fix this? any help would be much appreciated.</p>