startswith in Python

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*Memo for string, bytes and bytearray functions:

• My post explains replace().
• My post explains removeprefix() and removesuffix().
• My post explains endswith().

*Memo for a string, bytes and bytearray:

• My post explains a string.
• My post explains a bytes.
• My post explains a bytearray.

str.startswith() and bytes.startswith() or bytearray.startswith() can check if prefix is the prefix of the string and bytes or bytearray respectively between [start, end) as shown below:

*Memo:

• The 1st argument is prefix(Required-Type:str and tuple(str) for str.startswith() or Bytes-like object and typle(Bytes-like object) for bytes.startswith() and bytearray.startswith()):
  • It's the prefix of zero or more characters and bytes respectively.
  • If it's an empty string and bytes or bytearray respectively, True is returned.
  • Don't use prefix=.
• The 2nd argument is start(Optional-Type:int or NoneType):
  • It's a start index(inclusive).
  • If it's not set or None, 0 is set to it.
  • Don't use start.
• The 3rd argument is end(Optional-Type:int or NoneType):
  • It's an end index(exclusive).
  • If it's not set or None, the length + 1 is set to it.
  • Don't use end.

<String>:

v = 'hello world'

print(v.startswith('he'))             # True
print(v.startswith('he', None, None)) # True
print(v.startswith('HE'))             # False
print(v.startswith('wo'))             # False

print(v.startswith(('he', 'wo'))) # True
print(v.startswith(('wo', 'he'))) # True
print(v.startswith(('wo', 'lo'))) # False

print(v.startswith('he', 0)) # True
print(v.startswith('he', 1)) # False

print(v.startswith('he', 0, 1)) # False
print(v.startswith('he', 0, 2)) # True

print(v.startswith('wo', 6, 7)) # False
print(v.startswith('wo', 6, 8)) # True

print(v.startswith('')) # True

v = ''

print(v.startswith('')) # True

<Bytes & Bytearray>:

v = b'hello world'
v = bytearray(b'hello world')

print(v.startswith(b'he'))                        # True
print(v.startswith(bytearray(b'he')))             # True
print(v.startswith(b'he', None, None))            # True
print(v.startswith(bytearray(b'he'), None, None)) # True
print(v.startswith(b'HE'))                        # False
print(v.startswith(bytearray(b'HE')))             # False
print(v.startswith(b'wo'))                        # False
print(v.startswith(bytearray(b'wo')))             # False

print(v.startswith((b'he', b'wo')))                       # True
print(v.startswith((bytearray(b'he'), bytearray(b'wo')))) # True
print(v.startswith((b'wo', b'he')))                       # True
print(v.startswith((bytearray(b'wo'), bytearray(b'he')))) # True
print(v.startswith((b'wo', b'lo')))                       # False
print(v.startswith((bytearray(b'wo'), bytearray(b'lo')))) # False

print(v.startswith(b'he', 0))            # True
print(v.startswith(bytearray(b'he'), 0)) # True
print(v.startswith(b'he', 1))            # False
print(v.startswith(bytearray(b'he'), 1)) # False

print(v.startswith(b'he', 0, 1))            # False
print(v.startswith(bytearray(b'he'), 0, 1)) # False
print(v.startswith(b'he', 0, 2))            # True
print(v.startswith(bytearray(b'he'), 0, 2)) # True

print(v.startswith(b'wo', 6, 7))            # False
print(v.startswith(bytearray(b'wo'), 6, 7)) # False
print(v.startswith(b'wo', 6, 8))            # True
print(v.startswith(bytearray(b'wo'), 6, 8)) # True

print(v.startswith(b''))            # True
print(v.startswith(bytearray(b''))) # True

v = b''
v = bytearray(b'')

print(v.startswith(b''))
print(v.startswith(bytearray(b'')))
# True