Introduction to pandas

INTRODUCTION TO PANDAS
A LIBRARY THAT IS USED FOR DATA MANIPULATION AND ANALYSIS TOOL
USING POWERFUL DATA STRUCTURES

TYPES OF DATA STRUCTUE IN PANDAS
Data Structure Dimensions Description
Series 1 1D labeled homogeneous
array, sizeimmutable.
Data Frames 2 General 2D labeled, size-
mutable tabular structure
with potentially
heterogeneously typed
columns.
Panel 3 General 3D labeled, size-
mutable array.

SERIES
• Series is a one-dimensional array like structure with homogeneous
data. For example, the following series is a collection of integers 10,
23, 56,
• … 10 23 56 17 52 61 73 90 26 72

DataFrame
• DataFrame is a two-dimensional array with heterogeneous data. For
example,
Name Age Gender Rating
Steve 32 Male 3.45
Lia 28 Female 4.6
Vin 45 Male 3.9
Katie 38 Female 2.78

Data Type of Columns
Column Type
Name String
Age Integer
Gender String
Rating Float

PANEL
• Panel is a three-dimensional data structure with heterogeneous data.
It is hard to represent the panel in graphical representation. But a
panel can be illustrated as a container of DataFrame.

DataFrame
• A Data frame is a two-dimensional data structure, i.e., data is aligned
in a tabular fashion in rows and columns.
• Features of DataFrame
• Potentially columns are of different types
• Size – Mutable
• Labeled axes (rows and columns)
• Can Perform Arithmetic operations on rows and columns

pandas.DataFrame
pandas.DataFrame(data, index , columns , dtype , copy )

• data
• data takes various forms like ndarray, series, map, lists, dict, constants and also
another DataFrame.
• index
• For the row labels, the Index to be used for the resulting frame is Optional Default
np.arrange(n) if no index is passed.
• columns
• For column labels, the optional default syntax is - np.arrange(n). This is only true if
no index is passed.
• dtype
• Data type of each column.
• copy
• This command (or whatever it is) is used for copying of data, if the default is False.

• Create DataFrame
• A pandas DataFrame can be created using various inputs like −
• Lists
• dict
• Series
• Numpy ndarrays
• Another DataFrame

Example
• Example
• import pandas as pd
• Data = [_______]
• Df = pd.DataFrame(data)
• Print df
Example 2
Import pandas as pd
Data = {‘Name’ : [‘__’. ‘__’],’Age’: [___]}
Df = pd.DataFrame(data)
print df

Example
• data = [{'a': 1, 'b': 2},{'a': 5, 'b': 10, 'c': 20}]
• df = pd.DataFrame(data)
• print df
• ________________________________________
• data = [{'a': 1, 'b': 2},{'a': 5, 'b': 10, 'c': 20}]
• df = pd.DataFrame(data, index=['first', 'second'])
• print df

• data = [{'a': 1, 'b': 2},{'a': 5, 'b': 10, 'c': 20}]
• #With two column indices, values same as dictionary keys
• df1 = pd.DataFrame(data, index=['first', 'second'], columns=['a', 'b'])
• #With two column indices with one index with other name
• df2 = pd.DataFrame(data, index=['first', 'second'], columns=['a', 'b1'])
• print df1print df2

The following example shows how to create a DataFrame with
a list of dictionaries, row indices, and column indices.
• data = [{'a': 1, 'b': 2},{'a': 5, 'b': 10, 'c': 20}]
• #With two column indices, values same as dictionary keys
• df1 = pd.DataFrame(data, index=['first', 'second'], columns=['a', 'b'])
• #With two column indices with one index with other name
• df2 = pd.DataFrame(data, index=['first', 'second'], columns=['a', 'b1'])
• print df1
• print df2

Create a DataFrame from Dict of Series
• d = {'one' : pd.Series([1, 2, 3], index=['a', 'b', 'c']), 'two' : pd.Series([1,
2, 3, 4], index=['a', 'b', 'c', 'd'])}
• df = pd.DataFrame(d)
• print df

Column Addition
• d = {'one' : pd.Series([1, 2, 3], index=['a', 'b', 'c']), 'two' : pd.Series([1, 2,
3, 4], index=['a', 'b', 'c', 'd'])}
• # Adding a new column to an existing DataFrame object with column label
by passing new series
• print ("Adding a new column by passing as Series:")
• df['three']=pd.Series([10,20,30],index=['a','b','c'])
• print dfprint ("Adding a new column using the existing columns in
DataFrame:")
• df['four']=df['one']+df['three']
• print df

Column Deletion
• # Using the previous DataFrame, we will delete a
column
• # using del function
• d = {'one' : pd.Series([1, 2, 3], index=['a', 'b', 'c']),
'two' : pd.Series([1, 2, 3, 4], index=['a', 'b', 'c', 'd']),
'three' : pd.Series([10,20,30], index=['a','b','c'])}

• print ("Our dataframe is:")
• print df
• # using del function
• print ("Deleting the first column using DEL function:")
• del df['one']
• print df
# using pop function
• print ("Deleting another column using POP function:")
• df.pop('two')
• print df

Slicing in python
•import pandas as pd
d = {'one' : pd.Series([1, 2, 3], index=['a', 'b', 'c']),
'two' : pd.Series([1, 2, 3, 4], index=['a', 'b', 'c',
'd'])}
•df = pd.DataFrame(d)
•print df[2:4]

Addition of rows
• Df2 = pd.DataFrame([[5,6], [7,8]], columns = [‘a’, ‘b’])
• Df = df.append(df2 )
• Print df
Deletion of rows
• Df2 = pd.DataFrame([[5,6], [7,8]], columns = [‘a’, ‘b’])
• Df = df.drop(0)
• Print df

Reindexing
• import numpy as np
df1 =
pd.DataFrame(np.random.randn(10,3),columns=['col1','col2','col3'])
• df2 =
pd.DataFrame(np.random.randn(7,3),columns=['col1','col2','col3'])df1
= df1.reindex_like(df2)print df1

Concatenating objects
• One = pd.DataFrame({ ‘Name’: [‘__’] , ‘subject_id’: [‘__’], ‘marks’:
[‘__’]}, index = [] )
• two= pd.DataFrame({ ‘Name’: [‘__’] , ‘subject_id’: [‘__’], ‘marks’:
[‘__’]}, index = [] )
• Print pd.concat([one, two])

Handling categorical data
• There are many data that are repetitive for example gender , country , and codes are
always repetitive .
• Categorical variables can take on only a limited
• The categorical data type is useful in the following cases −
• A string variable consisting of only a few different values. Converting such a string
variable to a categorical variable will save some memory.
• The lexical order of a variable is not the same as the logical order (“one”, “two”,
“three”). By converting to a categorical and specifying an order on the categories,
sorting and min/max will use the logical order instead of the lexical order.
• As a signal to other python libraries that this column should be treated as a
categorical variable (e.g. to use suitable statistical methods or plot types).

• cat = pd.Categorical(['a', 'b', 'c', 'a', 'b', 'c'])
• print cat
• ____________________________________________
• import numpy as np
• cat = pd.Categorical(["a", "c", "c", np.nan], categories=["b", "a", "c"])
• df = pd.DataFrame({"cat":cat, "s":["a", "c", "c", np.nan]})
• print df.describe()
• print df["cat"].describe()

Introduction to pandas

More Related Content

What's hot (20)

Similar to Introduction to pandas (20)

Recently uploaded (20)

Introduction to pandas