python 删除空值且合并excel的操作

import xlrd
import pandas as pd
import openpyxl
target_xls = "合并表1.xlsx"
source_xls = ["全1.xlsx", "全2.xlsx","全3.xlsx",\
       "全4.xlsx","全5.xlsx","全6.xlsx"]
sysptoms=pd.DataFrame()
for i in range(len(source_xls)):
  print(i)#了解打印进度
  sheet2=pd.read_excel(source_xls[i]).fillna("")#有空格，填充函数，填的空值。要加fillna,不然无法删除空值所对应的行
  sysptom = sheet2[sheet2['电话'] !=""]#筛选
  sysptoms=pd.concat([sysptoms,sysptom])#两个dataframe合并,相当于合并excel
  print(type(sysptom))
  sysptoms.to_excel(target_xls, index=False)#pandas写入excel用.to_excel
print("ok")

infilename = r'D:\aajja.xlsx'
workbook = xlrd.open_workbook(infilename)
df = workbook.sheet_by_name('sheetname')
num_rows = df.nrows - 1 # 我这里是第一行不要，所以跳过了
num_cols = df.ncols
t = 0
im_data = np.zeros((num_rows, num_cols))
for curr_row in range(1, num_rows+1):
  for curr_col in range(num_cols):
    rawVal = df.cell(curr_row, curr_col).value
    if isinstance(rawVal, str):
      im_data[curr_row - 1, curr_col] = np.nan
    else:
      im_data[curr_row - 1, curr_col] = float(rawVal)

if isinstance(rawVal, str)