startswith in Python

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*Memo:

• My post explains string, bytes and bytearray functions.

str.startswith() and bytes.startswith() or bytearray.startswith() can check if prefix is the prefix of the string and bytes or bytearray respectively in the range [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 tuple(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-Default:None-Type:int/NoneType):
  • It's a start index(inclusive).
  • If it's None, the 1st index is set to it.
  • Don't use start.
• The 3rd argument is end(Optional-Default:None-Type:int/NoneType):
  • It's an end index(exclusive).
  • If it's None, the string and bytes or bytearray length are set to it respectively.
  • Don't use end.
• start and end can be signed indices(zero and positive and negative indices).
• Error doesn't occur even if [start, end) is out of the range [The 1st index, The string and bytes or bytearray length).

<String>:

v = 'hello world'

print(v.startswith('he'))             # True
print(v.startswith('he', None, None)) # True
print(v.startswith('he', -100, 100))  # 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', -11)) # True
print(v.startswith('he', 1))   # False
print(v.startswith('he', -10)) # False

print(v.startswith('he', 0, 1))     # False
print(v.startswith('he', -11, -10)) # False
print(v.startswith('he', 0, 2))     # True
print(v.startswith('he', -11, -9))  # True

print(v.startswith('wo', 6, 7))   # False
print(v.startswith('wo', -5, -4)) # False
print(v.startswith('wo', 6, 8))   # True
print(v.startswith('wo', -5, -3)) # 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', -100, 100))             # True
print(v.startswith(bytearray(b'he'), -100, 100))  # 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(b'he', -11))            # True
print(v.startswith(bytearray(b'he'), 0))   # True
print(v.startswith(bytearray(b'he'), -11)) # True
print(v.startswith(b'he', 1))              # False
print(v.startswith(b'he', -10))            # False
print(v.startswith(bytearray(b'he'), 1))   # False
print(v.startswith(bytearray(b'he'), -10)) # False

print(v.startswith(b'he', 0, 1))                # False
print(v.startswith(b'he', -11, -10))            # False
print(v.startswith(bytearray(b'he'), 0, 1))     # False
print(v.startswith(bytearray(b'he'), -11, -10)) # False
print(v.startswith(b'he', 0, 2))                # True
print(v.startswith(b'he', -11, -9))             # True
print(v.startswith(bytearray(b'he'), 0, 2))     # True
print(v.startswith(bytearray(b'he'), -11, -9))  # True

print(v.startswith(b'wo', 6, 7))              # False
print(v.startswith(b'wo', -5, -4))            # False
print(v.startswith(bytearray(b'wo'), 6, 7))   # False
print(v.startswith(bytearray(b'wo'), -5, -4)) # False
print(v.startswith(b'wo', 6, 8))              # True
print(v.startswith(b'wo', -5, -3))            # True
print(v.startswith(bytearray(b'wo'), 6, 8))   # True
print(v.startswith(bytearray(b'wo'), -5, -3)) # 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