CodeBlessU
learn code with examples

Create

Create boolean

Use direct assignment with True or False.

Use bool() function.

# Example, create bool
a1 = True
a2 = False
a3 = bool()

type(a1)

Create int

Create int

Use direct assignment with int literal (binary / octal / decimal / hex).

Use int() function.

# Example, create int
a1 = -1
a2 = 0
a3 = 5000
a4 = int()
a5 = 0b1111
a6 = 0O377
a7 = 0xff1100ab

type(a4)

Create int with specific base (2 to 35)

Say, you have number and its base known (2,8,10, 16 or any other, say 5), use int() function to create int.

# Example, create int with number 11 in base 2,8,10,16,5.
int_a = int("11", 2)
int_b = int("11", 8)
int_c = int("11", 10)
int_d = int("11", 16)
int_e = int("11", 5)
print(int_a, int_b, int_c, int_d, int_e) # prints 3 9 11 17 6

Create List

Create Empty List

List is created with empty square brackets.

Syntax:
variable = []

Empty list can also be created using list constructor/built-in function, list(). However, List Constructor is useful to create list from other iterable sources.

Syntax:
variable = list()
# Example, create empty list
countries = []

# Example, create list using built-in function, list()
countries = list()

type(countries)

Create List with initial elements

Initial elements can be provided with comma in between.

Syntax:
variable = [ item1, item2 ]
# Example, create list with initial elements
fruits = ["Apple", "Grapes"]

type(fruits)

Create tuple

Create empty tuple

Tuple is created with empty round brackets.

Syntax:
variable = ()

Empty tuple can also be created using tuple constructor/built-in function, tuple(). However, Tuple Constructor is useful to create tuple from other iterable sources.

Syntax:
variable = tuple()
# Example, create empty tuple
a = ()

# Example, create tuple using built-in function, tuple()
a = tuple()
type(a)

Create tuple with initial elements

Initial elements can be provided with comma in between.

Syntax:
variable = ( item1, item2 )

Or even without round brackets.

Syntax:
variable = item1, item2
# Example, create tuple with initial elements
a = (1, 2, 3)
type(a)

a = 1, 2, 3
a = 1,2,3
type(a)

a = tuple(1,2,3) # raises TypeError: tuple() takes at most 1 argument

Create tuple with only one element

If tuple contains only one element, Specify comma after the element.

Syntax:
variable = (element, )
variable = element, 

This is unique case. Specifying single element without comma (element ) is not interpreted as tuple. If comma is not specified, it leads to ambiguity whether its general expression or tuple? Hence provision for comma is done.

# Example, create tuple with only one element
a = (1,)
print(a)
type(a)

a = 1,
print(a)
type(a)

# what happens if comma not specified
a = (1) 
print(a)
type(a) # it is int!

Create array

Array type codes

Array type code is specified as char.

Typecode C data type Python data type
'b' signed char int
'h' signed short int
'i' signed int int
'l' signed long int
'q' signed long long int
'f' float float
'B' unsigned char int
'H' unsigned short int
'I' unsigned int int
'L' unsigned long int
'Q' unsigned long long int
'd' double float

Create int array

Python array supports char, short, int, long, long long, float and double - each with signed, unsigned. Python does not have all such data types, but python array facilitates user to specify it ONLY FOR array storage. Thanks to underlaying C implementation. It is specified by typecode.

To create array, use array.array() method.

Argument typecode is mandatory, initializer (sequence) is optional.

Syntax:
array.array( typecode [, initializer] )
Return Value:
array object
# Example, create array
import array

# second argument is tuple
some_numbers = array.array('i', (1, 2, 3, -3, -2, -1, 0) ) 
# array('i', [1, 2, 3, -3, -2, -1, 0])

# type 'q' - long long, second argument is list
a2 = array.array('q', [2**8, 2**16, 2**32, 2**60] )
# array('q', [256, 65536, 4294967296, 1152921504606846976])

Create empty array

# Example, create empty array
import array

a1 = array.array('l')
# array('l')

Create float array

# Example, create float array
import array

af1 = array.array('f', (2.1, 2.2, -10.5) )
# array('f', [2.0999999046325684, 2.200000047683716, -10.5]) 

OverflowError: Python int too large to convert to C long

Why this error:

Are you trying to add element in python array? And its size exceeding C data type restriction?

Solution:

While creating array, select type code as per matching need. OR

Ensure, that element to be inserted is following type code specific requirement.

# Example, try to create array with large number
import array

# type 'i' or 'l' causes OverflowError
a1 = array.array('i', (2**8, 2**16, 2**32, 2**60) ) # throws OverflowError: Python int too large to convert to C long
a1 = array.array('l', (2**8, 2**16, 2**32, 2**60) ) # throws OverflowError: Python int too large to convert to C long

# type 'h' - signed short
a1 = array.array('h')
a1.append(2**16) # throws OverflowError: signed short integer is greater than maximum

TypeError: integer argument expected, got float

Why this error:

Are you trying to add element whose type is not matching with array type code?

Solution:

While creating array, select type code as per matching need. OR

Ensure, that element to be inserted is following type code specific requirement.

# Example, try to append element with mismatch type
import array

a1 = array.array('i')
a1.append(1.01) # raises TypeError: integer argument expected, got float

a1 = array.array('i', (-1, 1, 0, 1.01 ) ) # raises TypeError: integer argument expected, got float

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