Lesson 1 Flashcards
(155 cards)
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INTEGRATIVE PROGRAMMING
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AND TECHNOLOGIES 2
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PYTHON PROGRAMMING
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Python Data Types
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• Variables can store data of different types
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and different types can do
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different things.
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• Python has the following data types built-in by default
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in these
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categories:
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GETTING THE DATA TYPE
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• You can get the data type of any object by using the type() function:
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SETTING THE DATA TYPE
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• In Python
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the data type is set when you assign a value to a variable:
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SETTING THE SPECIFIC DATA TYPE
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PYTHON NUMBERS
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• There are three numeric types in Python:
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• int
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float
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•
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Variable of numeric types are created when you assign a value to them:
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INT
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• Int
or integer
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unlimited length.
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FLOAT
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• Float
or "floating point number" is a number
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one or more.
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COMPLEX
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• Complex numbers are written with a "j" as the imaginary part:
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TYPE CONVERSION
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• You can convert from one type to another with the int()
float() and complex()
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methods
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NOTE
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• You cannot convert complex
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numbers into another number
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type.
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RANDOM NUMBER
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• Python does not have a random() function to make a random number
but
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Python has a built-in module called random that can be used to make random
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numbers:
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• Import the random module
and display a random number between 1 and 9:
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PYTHON CASTING (SPECIFY A VARIABLE TYPE)
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• There may be times when you want to specify a type on to a variable. This can
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be done with casting. Python is an object-orientated language
and as such it
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uses classes to define data types
including its primitive types.
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• Casting in python is therefore done using constructor functions:
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• int() - constructs an integer number from an integer literal
a float literal (by
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removing all decimals)
or a string literal (providing the string represents a
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whole number)
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• float() - constructs a float number from an integer literal
a float literal or a
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string literal (providing the string represents a float or an integer)
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• str() - constructs a string from a wide variety of data types
including strings
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integer literals and float literals
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INTEGERS
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FLOATS
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STRINGS
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PYTHON STRINGS
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• Strings in python are surrounded by either single quotation marks
or double
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quotation marks.
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• 'hello' is the same as "hello".
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• You can display a string literal with the print() function:
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STRINGS ARE ARRAYS
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• Like many other popular programming languages
strings in Python are arrays
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of bytes representing unicode characters.
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• However
Python does not have a character data type
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simply a string with a length of 1.
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• Square brackets can be used to access elements of the string.
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• Get the character at position 1 (remember that the first character has the
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position 0):
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LOOPING THROUGH STRING
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• Since strings are arrays
we can loop through the characters in a string
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for loop.
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• Loop through the letters in the word "banana":
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LOOPING THROUGH STRING
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• The len() function returns the length of a string:
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CHECK STRING
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• To check if a certain phrase or character is present in a string
we can use the
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keyword in.
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• Check if "free" is present in the following text:
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• Use it in an if statement:
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• Print only if "free" is present:
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CHECK IF NOT
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• To check if a certain phrase or character is NOT present in a string
we can use
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the keyword not in.
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• Check if "expensive" is NOT present in the following text:
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• Use it in an if statement:
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• print only if "expensive" is NOT present:
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SLICING STRINGS
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• You can return a range of characters by using the slice syntax.
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• Specify the start index and the end index
separated by a colon
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of the string.
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• Get the characters from position 2 to position 5 (not included):
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SLICING FROM THE START
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• By leaving out the start index
the range will start at the first character:
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• Get the characters from the start to position 5 (not included):
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SLICING TO THE END
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• By leaving out the end index
the range will go to the end:
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• Get the characters from position 2
and all the way to the end:
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NEGATIVE INDEXING
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• Use negative indexes to start the slice from the end of the string:
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• Get the characters:
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• From: "o" in "World!" (position -5)
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• To
but not included: "d" in "World!" (position -2):
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MODIFY STRINGS
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• The upper() method returns the string in upper case:
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• The lower() method returns the string in lower case:
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REMOVE WHITESPACE
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• Whitespace is the space before and/or after the actual text
and very often
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you want to remove this space.
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• The strip() method removes any whitespace from the beginning or the
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end:
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REPLACE STRINGS
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• The replace() method replaces a string with another string:
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SPLIT STRING
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• The split() method returns a list where the text between the specified
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separator becomes the list items.
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• The split() method splits the string into substrings if it finds instances of
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the separator:
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STRING CONCATENATION
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• To concatenate
or combine
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• Merge variable a with variable b into variable c:
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• To add a space between them
add a " ":
