Python Strings

A string is an inmutable sequence of characters.  This post covers string operations, including iteration, slicing, concatenation, comparison, string methods, and functions.

text = 'abc'
letter = text[0]

Iteration

text = 'abc'
for letter in text:
    print(letter)

Slicing

The start index is inclusive; the end index is exclusive.

If the end index goes beyond the end of the string, python will stop at the end of the string without throwing an error.

text = 'abcdef'
print(text[0:4]) --abcd
print(text[:4]) --abcd 

print(text[4:10]) --ef
print(text[4:]) --ef

print(text[:]) --abcdef

Concatenation

a = 'Hello '
b = a + 'there'
print(b) --Hello there

Contains Substring

text = 'abcd'
found = 'bc' in text 

print(found) --True

String Comparison

if first == second:
   print('Same string')

if first < second:
   print('First comes before second')

if first > second:
   print('First comes after second')

String Library

text = 'abcd'

upper = text.upper()
lower = upper.lower()

text.capitalize()

text.center(width)
text.center(width, fillChar)

text.strip()
text.lstrip()
text.rstrip()

text.endswith(suffix)

# Returns starting position if found or -1 if not found
text.find('bc') 
text.find(something, startingIndex)

# Replaces all instances if there is no count argument
text.replace(oldstr, newstr)
text.replace(oldstr, newstr, count)

Functions

• len(text): Length of a string
• type(text): Class type of text, which will return <class ‘str’> for a string
• dir(text): Returns a list of methods in the str class