title: Can't figure out why I keep getting a KeyError while trying to the number of a CSV row
body: <p>The code is super simple and the content of the cell is the exact same as what I'm writing into the code. Just trying to get the row number for all of the times where the ticker column = A.</p>
  <p>Code:</p>
  <pre><code>import pandas as pd
  
  filename = 'DataFiles/SHARADAR_SF1_aafe962511a67db10c0a72fe536305b0.csv'
  pattern = 'AAPL'
  
  df = pd.read_csv(filename, index_col=0)
  
  rows = df[df['ticker'] == pattern].index.to_list()
  </code></pre>
  <p>Example of the CSV (There are more tickers later in the file, for example AAPL or TSLA etc.):</p>
  <pre><code>ticker,dimension,calendardate,datekey,lastupdated,assets,assetsavg,cashneq,debt,debtc,debtusd,divyield,deposits,eps,epsusd,equity,equityavg,liabilities,netinc,pe,price,revenue
  A,ARQ,1999-12-31,2000-03-15,2020-09-01,7107000000,,1368000000,665000000,111000000,665000000,0,0,0.3,0.3,4486000000,,2621000000,131000000,,114.3,2246000000
  A,ARQ,2000-03-31,2000-06-12,2020-09-01,7321000000,,978000000,98000000,98000000,98000000,0,0,0.37,0.37,4642000000,,2679000000,166000000,,66,2485000000
  A,ARQ,2000-06-30,2000-09-01,2020-09-01,7827000000,,703000000,129000000,129000000,129000000,0,0,0.34,0.34,4902000000,,2925000000,155000000,46.877,61.88,2670000000
  A,ARQ,2000-09-30,2001-01-17,2020-09-01,8425000000,,996000000,110000000,110000000,110000000,0,0,0.67,0.67,5265000000,,3160000000,305000000,37.341,61.94,3372000000
  A,ARQ,2000-12-31,2001-03-19,2020-09-01,9208000000,,433000000,556000000,556000000,556000000,0,0,0.34,0.34,5541000000,,3667000000,154000000,21.661,36.99,2841000000
  </code></pre>