Python

Question 1

Attribute that returns data type for a series or dataframe

Answer 1

Series.dtype

Dataframe.dtype

Question 2

pandas method to show first n (5 is default) rows in a series

Answer 2

Series.head()

Question 3

pandas method to show last n (5 is default) rows in a series

Answer 3

Series.tail()

Question 4

pandas method to return unique values in a series

Answer 4

Series.unique()

Question 5

pandas method to view the highest and lowest values in a series with their counts

Answer 5

Series.sort_index()with ascending=True orFalse

Question 6

pandas method to count unique values in a series

Answer 6

Series.value_counts()
dropna=False includes null
normalize=True to do %

Question 7

pandas method to remove/replace specified text

Answer 7

Series.str.replace([‘text_to_replace’],’’)

Question 8

pandas method to cast a pandas object to a specified type (ex: cast string to float or int)

Answer 8

Series.astype(float)

Question 9

pandas method chaining to replace text and cast to number

Answer 9

Series.str.replace([‘text_to_replace’],’’).astype(float)

Question 10

pandas method to detect missing values and return a boolean same-sized object indicating if the values are NA.

Answer 10

Series.isnull()

Ex: Select null values in column
rev_is_null = f500[“revenue”].isnull()

Question 11

pandas method to detect existing (non-missing) values and return a boolean same-sized object indicating if the values are not NA.

Answer 11

Series.notnull()

Ex: Select non-null values in a column
rev_not_null = f500[f500[“revenue”].notnull()

Question 12

pandas method to generate descriptive statistics such as central tendency, dispersion and shape of a dataset’s distribution, excluding NaN values. Analyzes both numeric and object series, as well as DataFrame column sets of mixed data types. The output will vary depending on what is provided.

Answer 12

Series.describe()

include = ‘all’ to include non-numeric columns

Question 13

pandas method to rename series index labels or name.

Answer 13

Series.rename({“ram”:”ram_gb”}, axis = ‘columns’, inplace = True)

Question 14

pandas method to remove whitespace from start and end of string

Answer 14

String.strip()

Question 15

pandas method to convert string to lowercase

Answer 15

String.lower()

Question 16

pandas attribute that returns column names for dataframe

Answer 16

DataFrame.columns

Question 17

pandas method to print a concise summary of a DataFrame, including including the index dtype and column dtypes, non-null values and memory usage.

Answer 17

DataFrame.info()

Question 18

pandas method to remove or drop rows and columns with null values

Answer 18

DataFrame.dropna()
axis = 0 drops rows
axis = 1 drops columns

Question 19

pandas method to map values of Series according to input correspondence.

Used for substituting each value in a Series with another value, that may be derived from a function, a dict or a Series.

Answer 19

Series.map(mapping_dictionary)

Ex:
s = pd.Series([‘fox’, ‘cow’, np.nan, ‘dog’])
s.map({‘fox’: ‘cub’, ‘cow’: ‘calf’})

If a value from your series doesn’t exist as a key in your dictionary, it will convert that value to NaN

Question 20

pandas function to read in a csv file

Answer 20

f = pd.read_csv(‘[file_name]’, encoding=’[encoding_type]’)

encoding type examples = Latin-1, UTF-8, Windows-1251

Question 21

pandas method to export cleaned data (pandas)

Answer 21

DataFrame.to_csv(“file_name”, index=False)

Question 22

Attribute to access labels of a series

Answer 22

Series.index

Ex: Series.value_counts().head(10).index

Question 23

Sort a dictionary in ascending order based on values (not keys)

Answer 23

sort_d = sorted(dictionary.items(), key=lambda kv:(kv[1], kv[0])))

Question 24

pandas method to remove or drop rows or columns from a dataframe based on specified values

Answer 24

DataFrame.drop([“col_name1”, “col_name2”], axis=1)

 Change axis to 0 to drop rows

Question 25

Select portion of data between 2 values

Answer 25

DataFrame[DataFrame[“column”].between(min, max)]