All the IPython Notebooks in Python Introduction lecture series by Dr. Milaan Parmar are available @ GitHub
Python Literals¶
Literal is a raw data given in a variable or constant. In Python, there are various types of literals they are as follows:
1. Numeric Literals¶
Numeric Literals are immutable (unchangeable). Numeric literals can belong to 3 different numerical types Integer, Float and Complex.
Number data types in Python:
Integers: Integer(negative, zero and positive) numbers
- Example:
- ... -3, -2, -1, 0, 1, 2, 3 ...
- Example:
Floating Point Numbers(Decimal numbers)
- Example:
- ... -3.5, -2.25, -1.0, 0.0, 1.1, 2.2, 3.5 ...
- Example:
Complex Numbers
- Example:
- 1 + j, 2 + 3j, 1 - 1j
- Example:
# Example:
a = 0b1010 #Binary Literals
b = 100 #Decimal Literal
c = 0o310 #Octal Literal
d = 0x12c #Hexadecimal Literal
# Integer Literal
int_1 = 10
int_2 = 99
# Float Literal
float_1 = 10.5
float_2 = 1.5e2
# Complex Literal
x = 3.14j
print(a, b, c, d)
print(int_1, int_2)
print(float_1, float_2)
print(x, x.imag, x.real)
10 100 200 300 10 99 10.5 150.0 3.14j 3.14 0.0
In the above program
We assigned integer literals into different variables. Here,
ais binary literal,bis a decimal literal,cis an octal literal anddis a hexadecimal literal.When we print the variables, all the literals are converted into decimal values.
10.5and1.5e2are floating point literals.1.5e2is expressed with exponential and is equivalent to1.5 * 10^2.We assigned a complex literal i.e
3.14jin variablex. Then we use imaginary literal (x.imag) and real literal (x.real) to create imaginary and real part of complex number.
To learn more about Numeric Literals, refer to Python Numbers.
Type Conversion of Numbers in Python¶
As a programmer, you can convert a variable of any data type to Number data types in Python using the below Python inbuilt functions. Also, using these functions, you can convert a number from one Number data type to another i.e from int to float, float to decimal, decimal to int and so on.
int (): This function converts any data type to integer data type.float (): This function converts any data type to float data type.complex (real, imaginary)orcomplex (real): This function converts any data type to complex data type.
Note: There is no 'long' integer in Python 3, int and long are unified now. This means int behave more like long. Sample program showing type conversion of Numbers in Python
# Example:
a = 3.7
b = 19.16
c = 3 + 27j
#converting float to int
print (int(b))
#converting int to float
print (float(a))
#converting int to complex
print (complex(a))
#converting float to complex
print (complex(b))
#converting to complex
print (complex(a, b))
19 3.7 (3.7+0j) (19.16+0j) (3.7+19.16j)
2. String literals (unicode character strings)¶
A string literal is a sequence of characters surrounded by quotes. We can use both single, double or triple quotes for a string. And, a character literal is a single character surrounded by single or double quotes.
# Example:
a = '''Apple'''
b = """Apple"""
c = 'Apple'
d = "Apple"
e = Apple # cannot write string with out quotes ('', " ", """ """, ''' ''')
print(a)
print(b)
print(c)
print(d)
print(e)
--------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-3-ee80ca1a52c8> in <module> 9 d = "Apple" 10 ---> 11 e = Apple # cannot write string with out quotes ('', " ", """ """, ''' ''') 12 13 print(a) NameError: name 'Apple' is not defined
# Example:
strings = "This is Python"
char = "C"
multiline_str = """This is a multiline string with more than one line code."""
unicode = u"\u00dcnic\u00f6de"
raw_str = r"raw \n string"
print(strings)
print(char)
print(multiline_str)
print(unicode)
print(raw_str)
This is Python C This is a multiline string with more than one line code. Ünicöde raw \n string
In the above program,
This is Pythonis a string literal andCis a character literal.The value with triple-quote """ assigned in the
multiline_stris multi-line string literal.The
u"\u00dcnic\u00f6de"is a unicode literal which supports characters other than English. In this case,\u00dcrepresentsÜand\u00f6representsö.r"raw \n string"is a raw string literal.
3. Boolean literals¶
A Boolean literal can have any of the two values: True or False.
# Example:
#REMEMBER True == 1 False == 0
x = (1 == True)
y = (1 == False)
a = True + 6
b = False + 90
print("x is", x)
print("y is", y)
print("a:", a)
print("b:", b)
x is True y is False a: 7 b: 90
In the above program, we use boolean literal True and False. In Python, True represents the value as 1 and False as 0. The value of x is True because 1 is equal to True. And, the value of y is False because 1 is not equal to False.
Similarly, we can use the True and False in numeric expressions as the value. The value of a is 6 because we add True which has value of 1 with 6. Similarly, b is 90 because we add the False having value of 0 with 90.
# Example:
9.0 # a simple floating point number
1e100 # a googol as floating point number
-1234567890 # an integer
True or False # the two possible boolean values
'This is a string'
"It's another string"
print("""Triple quotes (also with '''), allow strings to break over multiple lines.
Alternatively \n is a newline character (\t for tab, \\ is a single backslash)""")
Triple quotes (also with '''), allow strings to break over multiple lines. Alternatively is a newline character ( for tab, \ is a single backslash)
Python also has complex numbers that can be written as follows. Note that the ( ) brackets or parentheses are required.
complex_number1 = complex(1,2)
print(complex_number1)
complex_number2 = (1.0+2j) # the same number as above
print(complex_number2)
(1+2j) (1+2j)
Special literals¶
Python contains one special literal i.e., None. We use it to specify to that field that is not created.
# Example:
juice = "Available"
soup = None
def menu(x):
if x == juice:
print(juice)
else:
print(soup)
menu(juice)
menu(soup)
Available None
In the above program, we define a menu function. Inside menu, when we set parameter as drink then, it displays Available. And, when the parameter is food, it displays None.
Literal Collections¶
There are four different literal collections List literals, Tuple literals, Dict literals, and Set literals.
# Example:
fruits1 = ("Banana", "Apple", "Strawberry") # tuple ()
fruits2 = ["Banana", "Apple", "Strawberry"] # list []
fruits3 = {"Banana", "Apple", "Strawberry"} # set {}
fruits4 = {"1":"Banana", "2":"Apple", "3":"Strawberry"} # dictionary {"Key":"Value"}
print(fruits1)
print(fruits2)
print(fruits3)
print(fruits4)
('Banana', 'Apple', 'Strawberry')
['Banana', 'Apple', 'Strawberry']
{'Apple', 'Strawberry', 'Banana'}
{'1': 'Banana', '2': 'Apple', '3': 'Strawberry'}
# Example:
fruits = ["apple", "mango", "orange"] #list
numbers = (1, 2, 3) #tuple
alphabets = {'a':'apple', 'b':'ball', 'c':'cat'} #dictionary
vowels = {'a', 'e', 'i' , 'o', 'u'} #set
print(fruits)
print(numbers)
print(alphabets)
print(vowels)
['apple', 'mango', 'orange']
(1, 2, 3)
{'a': 'apple', 'b': 'ball', 'c': 'cat'}
{'u', 'e', 'o', 'a', 'i'}
In the above program, we created a list of fruits, tuple of numbers, dictionary dict having values with keys desginated to each value and set of vowels.
Note: To learn more about literal collections, refer to Python Data Types.