23  strings

Strings are defined using either double quotes “” or single quotes. ’’

name1 = "Atilla"
name2 = 'Atilla'

If we need to use single quote inside a string enclosed by single quotes, we need to escape it using backslash  character. Like below:

name2 = 'Atilla\'s Car'

To avoid using escape characters, it is recommended that:

Multiline string are defined using 3 quotes.

multi_line_string1 = """ Hello
    this is multi line string
"""

multi_line_string2 = ''' Hello
    this is another multi line string
'''

To change other variable to string, we use str function

a = 5
print("number is " + str(a))

23.0.0.1 String Formatting

Python 3.6 introduced f-strings for easy string formatting. We will use them in our classes. Variable name is enclosed between curly braces in the string.

age = 42
print(f"Age is {age}")

output is

Age is 42

23.0.0.2 Common string methods

since strings are immutable in python, all of the methods returns a modified string and do not modify original string.

- lower()  lowercase
- upper()  lowercase
- strip()  strips whitespace from both sides of string
- lstrip  strips whitespace from left side of string
- rstrip  strips whitespace from right side of string

count(substring) how many time substring occurs
isnumeric()
isalpha() True if only alphabetic characters exists
split(), split(delimiter)   return list of substrings, splited by whitespace/delimiter

23.0.0.3 Common string operations/functions

len(string)
    Returns the length of the string
for character in string:
    # do something

    iterates over character in string

substring in string  return True if substring in string

string[i] we can use list indexing with string.

see [all string methods](https://docs.python.org/3/library/stdtypes.html#string-methods)

In [1]: name = “atilla”

In [2]: len(name) Out[2]: 6

In [3]: for ch in name: …: print(ch) …: a t i l l a

In [4]: “t” in name Out[4]: True

In [5]: “x” in name Out[5]: False

In [6]: name[0] Out[6]: ‘a’

In [7]: name[-1] Out[7]: ‘a’

In [8]: name[2:4] Out[8]: ‘il’

In [9]: name[2:5] Out[9]: ‘ill’

In [10]: name[2:6] Out[10]: ‘illa’

23.1 More

23.3 Video Tutorials