Light DataFrame

A light and user-friendly data structure with convenient filter used to process csv files or tables.

Quick Example

from DataFrame import DataFrame

• print orders made in Oct. 2017/2018 sorted by price:

df = DataFrame.read_csv("orders.csv")
df.select.where("date").contain("2017-10").Or.contain("2018-10")().sort("price").print()

• set field "important" as "False" for all rows whose "price" field value is less than 300:

df.update("important", False).where("price").less(300)()

• save orders settled in USD with price greater than $1000 to a new csv file:

df.select.where("settlement").equal("USD").where("price").greater(1000)().save_csv("some_orders.csv")

Usage

• import

from DataFrame import DataFrame

• read csv

df = DataFrame.read_csv(csv_path)

• load matrix(nested list)

head = ["name", "time", "value"]
matrix = [["Tom", 1987, 15], ["Jerry", 1993, 32]]
df = DataFrame.read_matrix(head, matrix)

• select / add / modify / pop row

df_row = df[3]  # get a dataframe formed by the 4th row (return DataFrame)
df_rows = df[[1,3,5,7,9]]  # get a dataframe formed by these 5 rows (return DataFrame)
row = df.rows[2]  # get the third row (return list)
d = df.dict(5)  # get the sixth row in the form of dict (return dict)
dicts = df.dict()  # get all rows in the form of dict (return list)
df.append(new_row)  # append new row
df.append({"col_1": 2, "col_2": 3})  # append new row in the form of dict
df[0] = [34, "True", "Tony"]  # update the first row
df.pop(row_num)  # pop, equivalent to df.rows.pop(row_num=None)

• select / add / modify column

name_list = df["name"]  # get a list
extract_df = df[["description", "value"]]  # get a new DataFrame object with two columns
df["name"] = ["Mary", "Kevin"]  # replace whole column
df["sex"] = ["F", "M"]  # add a new column

• query/update with conditions

# finding rows where age > 16, sex = "M"
df = df.select.where("age").greater(16).where("sex").equal("M")()

# finding rows where name contains "iphone", price is between 6000 and 9000, release in 2017 or 2018
df = df.select.where("name").contain("iphone").where("price").between(6000, 9000)()
df = df.select.where("release date").contain("2017").Or.contain("2018")()
  
# Note: ".Or" is inferior to ".where(feature).<operator>(cond)", for example,
# df.select.where("A").greater(1).where("B").prefix("cn").Or.where("C").postfix("uw").where("D").less(9)()
# is equivalent to finding rows satisfying "(A > 1 and B prefix "cn") or (C postfix "uw" and D < 9)"

# finding rows where id don't have prefix "AHU", then print 20 results
df.select.where("id").Not.prefix("AHU")().print(20)

# update the "is_retired" field on condition that the "age" field is greater than 65
df.update("is_retired", True).where("age").greater(65)()

• sort by column

# sort by age
df.sort("age")

# sort by price reversedly
df.sort("price", reverse=True)

• concat two DataFrame objects

df = df_1 + df_2

• merge two DataFrame objects (eliminate all repeated rows)

df.merge(another_df)

• get difference of two DataFrame objects

df = df_1 - df_2

• map / apply function on column

df.map(lambda dt: dt.split()[0], "time")
df.map(float, "price")

• save csv and append new content to existed csv file

df.save_csv(csv_path)
df.append_csv(csv_path)