Python中使用Pandas与Series进行数据集挖掘的技术问题咨询

Hey there! Let's work through your two pandas questions step by step:

Your current code df_test.get_value(30, 'Major') might work in some cases, but there are better (and more future-proof) ways to do this, plus we need to clarify a key detail about your DataFrame structure:

• If FIDN is your row index (i.e., the index labels are the FIDN values):
  The get_value() method is actually deprecated in newer pandas versions (since 0.21.0). Instead, use .loc[] or .at[]—these are more explicit and widely recommended:

  # Using loc (works for single values or ranges)
  df_test.loc[30, 'Major']
  # Using at (faster for single value lookups)
  df_test.at[30, 'Major']
  

• If FIDN is a regular column (not the index):
  Your current approach won't work because get_value() uses position-based indexing, not column values. Instead, filter the DataFrame to find rows where FIDN equals 30, then extract the Major:

  # Returns a Series with the matching Major(s)
  df_test.loc[df_test['FIDN'] == 30, 'Major']
  # If you know there's exactly one match, get the single value
  df_test.loc[df_test['FIDN'] == 30, 'Major'].iloc[0]
  

Your code df_test.sort_values( ['LastName', 'tuition'] ) has the right syntax, but the issue is likely one of two things:

Reason 1: You're not capturing the sorted result #

By default, sort_values() returns a new sorted DataFrame instead of modifying the original one. If you just run the line without assigning it to a variable or using inplace=True, you might only see a truncated preview (which could look like just column names/index). Fix this by either:

# Option 1: Assign to a new variable
sorted_students = df_test.sort_values( ['LastName', 'tuition'] )
# Now view the sorted data
print(sorted_students)

# Option 2: Modify the original DataFrame in-place
df_test.sort_values( ['LastName', 'tuition'], inplace=True )

Reason 2: Tuition is stored as a string (not a number) #

If your tuition column has string values (e.g., with $ signs or commas like "$10,000"), sorting will use lexicographical order (not numeric), which might make it look like the sort didn't work. First convert it to a numeric type:

# Remove non-numeric characters and convert to float
df_test['tuition'] = df_test['tuition'].str.replace(r'[$,]', '', regex=True).astype(float)
# Now sort as before
sorted_students = df_test.sort_values( ['LastName', 'tuition'] )

内容的提问来源于stack exchange，提问作者Ryan1997123