Python Keywords, Identifiers and Statements 14

Python Strings

String is sequence of Unicode characters. We can use single quotes or double quotes to represent strings. Multi-line strings can be denoted using triple quotes, ”’ or “””.

>>> s = ‘This is a string’
>>> s = “This is a string”
>>> s = ”’a multiline
text ”’
>>> s=””” Hello this is multiline
text”””
Like list and tuple, slicing operator [ ] can be used with string. Strings are immutable(cannot be modified).

Example:1

s = 'Hello world!'
print(s)
print(s[0])
print(s[1])
print("s[4] = ", s[4])
print("s[6:11] = ", s[6:11])
# Generates error
# Strings are immutable in Python
#s[5] ='d'

Output:

Hello world!
H
e
s[4] =  o
s[6:11] =  world
>>> 

Python Dictionary

Dictionary is an unordered collection of key-value pairs. It is generally used when we have a huge amount of data. Dictionaries are optimized for retrieving data. We must know the key to retrieve the value.
In Python, dictionaries are defined within braces {} with each item being a pair in the form key:value. Key and value can be of any type.

>>> d = {1:’value’,’key’:2}
>>> type(d)
<class ‘dict’>

We use key to retrieve the respective value. But not the other way around.

example:1:

d = {1:'one',2:'two',3:'three',4:'four',5:'five'}
print(type(d))
print(d)

Output:

<class 'dict'>
{1: 'one', 2: 'two', 3: 'three', 4: 'four', 5: 'five'}
>>> 

Example:2

d = {1:'one',2:'two',3:'three',4:'four',5:'five'}
print(type(d))
print(d)

print("d[1] = ", d[1]);
print("d[2] = ", d[2]);
print("d[3] = ", d[3]);
print("d[4] = ", d[4]);
print("d[5] = ", d[5]);

Output:

<class 'dict'>
{1: 'one', 2: 'two', 3: 'three', 4: 'four', 5: 'five'}
d[1] =  one
d[2] =  two
d[3] =  three
d[4] =  four
d[5] =  five
>>> 

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