*Memos:
- My post explains str().
- My post explains a byte string.
- My post explains encode(), decode() and a byte string.
- My post explains upper(), lower(), casefold() and swapcase() with a string and byte string.
- My post explains title(), capitalize(), isupper(), islower() and istitle() with a string and byte string.
- My post explains count(), startswith() and endswith().
- My post explains find(), rfind(), index() and rindex().
- My post explains replace(), removeprefix(), removesuffix() and join().
- My post explains split() and rsplit().
- My post explains splitlines(), partition() and rpartition().
- My post explains center(), ljust() and rjust().
- My post explains zfill() and expandtabs().
- My post explains strip(), lstrip(), rstrip() and isspace().
- My post explains maketrans() and translate().
- My post explains isdecimal(), isdigit() and isnumeric().
- My post explains isalpha(), isalnum(), isascii(), isprintable(), isidentifier(), iskeyword() and issoftkeyword().
- My post explains format().
- My post explains format_map().
- My post explains f-strings.
A string:
- is the sequence of zero or more characters whose type is
str. - is immutable so it cannot be changed.
- can be created by the string literal
'',"",''''''or""""""or str() with or without any types of objects: *Memos:- A string literal can have a lot of Unicode characters.
- A string literal can also be used for a docstring.
-
''or""is for one line. -
''''''or""""""is for one or more lines.
- can be enlarged with
*and a number. - can be accessed but cannot be changed by indexing or slicing.
Be careful, a huge string gets I/O error.
'' or "" can create the string which is a sequence of zero or more characters as shown below. *\' is the escape sequence to output ':
v = '' # Empty string
v = "Hello World"
v = "Lёт's gφ!" # Let's go!
v = "I'm John."
v = 'I\'m John.'
v = '''I'm John.'''
v = """I'm John."""
v = '''Apple Orange Banana Kiwi'''
v = 'Apple' " Orange" '''Banana''' """Kiwi"""
v = '''Apple
Orange
Banana
Kiwi'''
v = """
Apple
Orange
Banana
Kiwi
"""
'These above get no error'
"These above get no error"
'''These above get no error'''
"""These above get no error"""
'''
These above
get no error
'''
"""
These above
get no error
"""
print(type('Hello World'))
print(type(str('Hello World')))
# <class 'str'>
v = '' # Empty string
print(v)
# Nothing
v = "Hello World"
print(v)
# Hello World
v = "Lёт's gφ!" # Let's go!
print(v)
# Lёт's gφ!
v = "I'm John."
v = 'I\'m John.'
v = '''I'm John.'''
v = """I'm John."""
print(v)
# I'm John.
v = '''Apple Orange Banana Kiwi'''
v = 'Apple' " Orange" ''' Banana''' """ Kiwi"""
print(v)
# Apple Orange Banana Kiwi
v = '''Apple
Orange
Banana
Kiwi'''
print(v)
# Apple
# Orange
# Banana
# Kiwi
v = """
Apple
Orange
Banana
Kiwi
"""
print(v)
#
# Apple
# Orange
# Banana
# Kiwi
#
A string can be enlarged with * and a number as shown below:
v = 'abc' * 3
print(v)
# abcabcabc
Be careful, a huge string gets I/O error as shown below:
v = 'abc' * 100000000
print(v)
# OSError: [Errno 29] I/O error
You can access a string by indexing or slicing as shown below:
v = 'abcdefgh'
print(v)
# abcdefgh
print(v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7])
print(v[-8], v[-7], v[-6], v[-5], v[-4], v[-3], v[-2], v[-1])
# a b c d e f g h
v = 'abcdefgh'
print(v[:])
print(v[::])
# abcdefgh
print(v[::2])
# aceg
print(v[::-2])
# hfdb
print(v[2:])
print(v[-6:])
print(v[2::])
print(v[-6::])
# cdefgh
print(v[2::2])
print(v[-6::2])
# ceg
print(v[2::-2])
print(v[-6::-2])
# ca
print(v[:6])
print(v[:-2])
print(v[:6:])
print(v[:-2:])
# abcdef
print(v[:6:2])
print(v[:-2:2])
# ace
print(v[:6:-2])
print(v[:-2:-2])
# h
print(v[2:6])
print(v[-6:-2])
print(v[2:6:])
print(v[-6:-2:])
# cdef
print(v[2:6:2])
print(v[-6:-2:2])
# ce
print(v[2:6:-2])
print(v[-6:-2:-2])
# Empty string
You cannot change a string because it's immutable as shown below. *A del statement can still be used to remove a variable itself:
v = 'abcdef'
v[0] = 'X'
# v[-6] = 'X'
v[2:6] = ['Y', 'Z']
# TypeError: 'str' object does not support item assignment
v = 'abcdef'
del v[0]
# del v[-6]
del v[3:5]
# TypeError: 'str' object does not support item deletion
v = 'abcdef'
del v
print(v)
# NameError: name 'v' is not defined
If you really want to change a string, use list() and join() as shown below. *join() can concatenate the zero or more strings in an iterable.
v = 'abcdef'
v = list(v)
v[0] = 'X'
# v[-6] = 'X'
v[2:6] = ['Y', 'Z']
v = ''.join(v)
print(v)
# XbYZ
v = 'abcdef'
v = list(v)
del v[0]
# del v[-6]
del v[3:5]
v = ''.join(v)
print(v)
# bcd
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