old_contents: import numpy as np
  import pandas as pd
  
  # ------------------------------------------------------------------------------
  
  print(f"Starting ... {int(time.time())}");
  
  timestamps = pd.date_range("1970-01-01", "2019-08-15", freq='S')
  df = pd.DataFrame({"timestamp": timestamps,
                     "normal": np.random.normal(size=len(timestamps)),
                     "log_normal": np.random.lognormal(size=len(timestamps)),
                     "exponential": np.random.exponential(size=len(timestamps)),
                     })
  df.set_index("timestamp")
  
  print(f"All memory allocations are done. Calculating means ... {int(time.time())}")
  
  m1: float = df["normal"].mean()
  m2: float = df["log_normal"].mean()
  m3: float = df["exponential"].mean()
  print(f"{m1}, {m2}, {m3}")
  print(f"{int(time.time())} ... Done");
  
  # ------------------------------------------------------------------------------
  
  # Local Variables:
  # mode:Python
  # tab-width:4
  # c-basic-offset:4
  # End:
  
  
new_contents: import time
  import numpy as np
  import pandas as pd
  
  # ------------------------------------------------------------------------------
  
  print(f"Starting ... {int(time.time())}");
  
  timestamps = pd.date_range("1970-01-01", "2019-08-15", freq='S')
  df = pd.DataFrame({"timestamp": timestamps,
                     "normal": np.random.normal(size=len(timestamps)),
                     "log_normal": np.random.lognormal(size=len(timestamps)),
                     "exponential": np.random.exponential(size=len(timestamps)),
                     })
  df.set_index("timestamp")
  
  print(f"All memory allocations are done. Calculating means ... {int(time.time())}")
  
  m1: float = df["normal"].mean()
  m2: float = df["log_normal"].mean()
  m3: float = df["exponential"].mean()
  print(f"{m1}, {m2}, {m3}")
  print(f"{int(time.time())} ... Done");
  
  # ------------------------------------------------------------------------------
  
  # Local Variables:
  # mode:Python
  # tab-width:4
  # c-basic-offset:4
  # End:
  
  
subject: Fix import error in pandas_performance.py