The data is usually described as a certain type. This type determines what you can do with the data and how the data is stored. In Python basic types are integers (. int. ), floating point (float), strings and Booleans. ID: 699809
DownloadNote - The PPT/PDF document "Data Types Data Types Every program must..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Presentations text content in Data Types Data Types Every program must deal with data
Slide1
Data Types
Slide2
Data Types
Every program must deal with data
The data is usually described as a certain type
This type determines what you can do with the data and how the data is stored
In Python basic types are integers (
int
), floating point (float), strings and Booleans
The first two are numeric and can be used in arithmetic, the last two are not
Slide3
Integers vs. Floating point
Integers are numbers which have no decimals, no fractions
They can be positive, negative, zero
Python can handle numbers of
very,
very large magnitude
Floating point numbers are ones which have fractions, like 3.14 and 2.0 and 5.2983841983
They are stored differently in the computer and their arithmetic is done differently
Slide4
Floating point numbers - storage
Each floating point number is stored in several pieces. You can think of one as being written in scientific notation, like
3.592 x 10
2
= 359.2
In Python this is written as 3.592e2 (the base is assumed to be 10)
The 3.592 is the
mantissa
The 2 is the power or exponent – it can be positive or negative. Positive powers make numbers larger, negative powers make numbers smaller (towards zero)
Example: 4.923e-3 = 0.004923
Example: 7.2341e10 =
72341000000
Slide5
Floating point numbers – arithmetic
When you add numbers with decimals together, you must “align the decimals” so you are adding tenths to tenths, hundredths to hundredths and so on
The computer does the same thing behind the scenes
So floating point arithmetic is usually slower than integer arithmetic
Floating point numbers also have an inherent error in them, just because a lot of numbers cannot be stored precisely in the machine (think of pi or 1/3). Even 0.1 is not precise inside the computer – in binary it is a repeating decimal!
Most calculations are not too much affected by this but you should be aware of it. If your work depends on many decimal places of accuracy, be careful how you use floating point numbers!
Slide6
Strings
These data items are delimited by quotes, either single quotes (‘) or double quotes (“)
(Delimited by means that they are enclosed by the quotes, marked off by the quotes)
We will use them in many ways
simply as labels “Total of numbers”
variables like names and address
input data
Examples: “Joe”, “12345923 adfa123.s8234&*”, “”, ‘”hi” he said’
Slide7
Booleans
Named after George
Boole,
English
mathematician
, logician
Created Boolean algebra, a two-valued logic based on True and False
The basis of all computer circuits (see EE 280)
In Python the Boolean constants are True and False – note that these are not strings – no quotes
They can be assigned to variables, they can be output
They are used most often with if statements, chapter 6
Download this presentation
DownloadNote - The PPT/PDF document "Data Types Data Types Every program must..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Presentations text content in Data Types Data Types Every program must deal with data
Data Types
Slide2Data Types
Every program must deal with data
The data is usually described as a certain type
This type determines what you can do with the data and how the data is stored
In Python basic types are integers (
int
), floating point (float), strings and Booleans
The first two are numeric and can be used in arithmetic, the last two are not
Slide3Integers vs. Floating point
Integers are numbers which have no decimals, no fractions
They can be positive, negative, zero
Python can handle numbers of
very,
very large magnitude
Floating point numbers are ones which have fractions, like 3.14 and 2.0 and 5.2983841983
They are stored differently in the computer and their arithmetic is done differently
Slide4Floating point numbers - storage
Each floating point number is stored in several pieces. You can think of one as being written in scientific notation, like
3.592 x 10
2
= 359.2
In Python this is written as 3.592e2 (the base is assumed to be 10)
The 3.592 is the
mantissa
The 2 is the power or exponent – it can be positive or negative. Positive powers make numbers larger, negative powers make numbers smaller (towards zero)
Example: 4.923e-3 = 0.004923
Example: 7.2341e10 =
72341000000
Slide5Floating point numbers – arithmetic
When you add numbers with decimals together, you must “align the decimals” so you are adding tenths to tenths, hundredths to hundredths and so on
The computer does the same thing behind the scenes
So floating point arithmetic is usually slower than integer arithmetic
Floating point numbers also have an inherent error in them, just because a lot of numbers cannot be stored precisely in the machine (think of pi or 1/3). Even 0.1 is not precise inside the computer – in binary it is a repeating decimal!
Most calculations are not too much affected by this but you should be aware of it. If your work depends on many decimal places of accuracy, be careful how you use floating point numbers!
Slide6Strings
These data items are delimited by quotes, either single quotes (‘) or double quotes (“)
(Delimited by means that they are enclosed by the quotes, marked off by the quotes)
We will use them in many ways
simply as labels “Total of numbers”
variables like names and address
input data
Examples: “Joe”, “12345923 adfa123.s8234&*”, “”, ‘”hi” he said’
Slide7Booleans
Named after George
Boole,
English
mathematician
, logician
Created Boolean algebra, a two-valued logic based on True and False
The basis of all computer circuits (see EE 280)
In Python the Boolean constants are True and False – note that these are not strings – no quotes
They can be assigned to variables, they can be output
They are used most often with if statements, chapter 6