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Super Kai (Kazuya Ito)
Super Kai (Kazuya Ito)

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String in Python (2)

#python #string #str #function

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*Memo:

str() can create a string with or without many types of values or can decode a byte string to a string as shown below:

*Memo:

  • The 1st argument is object(Optional-Default:''-Type:Any or Default: b''-Type:Bytes-like object):
    • If encoding and/or errors are/is set, it must be a bytes-like object to decode and its default value is b'', working as decode().
  • The 2nd argument is encoding(Optional-Default:'utf-8'-Type:str):
    • 'utf-8', 'utf-7', 'utf-16', 'big5', 'ascii', etc can be set to it.
    • You can see Standard Encodings for more possible values.
  • The 3rd argument is errors(Optional-Default:'strict'-Type:str):
    • It controls decoding error with the error handlers, 'strict', 'ignore', 'replace', 'xmlcharrefreplace', 'backslashreplace', etc.
    • 'strict' raises UnicodeError if the character or byte, which cannot be encoded or decoded, exists.
    • 'ignore' ignores the character or byte which cannot be encoded or decoded.
    • 'replace' replaces the character or byte, which cannot be encoded or decoded, with ? for encoding or � for decoding.
    • 'xmlcharrefreplace' replaces the character, which cannot be encoded, with the XML/HTML numeric character reference format &#num;:
      • It doesn't support decoding so error occurs for the byte which cannot be decoded while error doesn't occur for the byte which can be decoded.
    • 'backslashreplace' replaces the character or byte, which cannot be encoded or decoded, with the hexadecimal format \xhh, \uxxxx or \Uxxxxxxxx for encoding or \xhh for decoding.
    • You can see more error handlers.
    • You can create your own error handler with codecs.register_error().

<Create a string>: 

v = str()                                # Empty str
v = str(object='')                       # Empty str
v = str(object='12')                     # str
v = str(object=b'12')                    # bytes
v = str(object=bytearray(b'12'))         # bytearray
v = str(object=12)                       # int
v = str(object=1.2)                      # float
v = str(object=1.2+3.4j)                 # complex
v = str(object=True)                     # bool
v = str(object=[1, 2, 3])                # list
v = str(object=(1, 2, 3))                # tuple
v = str(object={1, 2, 3})                # set
v = str(object=frozenset({1, 2, 3}))     # frozenset
v = str(object={'name':'John'})          # dict
v = str(object={'name':'John'}.keys())   # dict.keys()
v = str(object={'name':'John'}.values()) # dict.values()
v = str(object={'name':'John'}.items())  # dict.items()
v = str(object=iter([1, 2, 3]))          # iterator
v = str(object=range(1, 4)               # range
v = str(object=lambda: 10)               # function
# No errors
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# Empty str
print(str())
print(str(object=''))
# Nothing
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v = str(object='12') # str

print(v, v[0], v[1])
# 12 1 2
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v = str(object=b'12') # bytes

print(v, v[0], v[1], v[2], v[3], v[4])
# b'12' b ' 1 2 '
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v = str(object=bytearray(b'12')) # bytearray

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# bytearray(b'12') b y t e a r r a y (
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v = str(object=12) # int

print(v, v[0], v[1])
# 12 1 2
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v = str(object=1.2) # float

print(v, v[0], v[1], v[2])
# 1.2 1 . 2
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v = str(object=1.2+3.4j) # complex

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# (1.2+3.4j) ( 1 . 2 + 3 . 4 j )
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v = str(object=True) # bool

print(v, v[0], v[1], v[2], v[3])
# True T r u e
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v = str(object=[1, 2, 3]) # list

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8])
# [1, 2, 3] [ 1 ,   2 ,   3 ]
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v = str(object=(1, 2, 3)) # tuple

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8])
# (1, 2, 3) ( 1 ,   2 ,   3 )
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v = str(object={1, 2, 3}) # set

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8])
# {1, 2, 3} { 1 ,   2 ,   3 }
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v = str(object=frozenset({1, 2, 3})) # frozenset

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# frozenset({1, 2, 3}) f r o z e n s e t (
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v = str(object={'name':'John'}) # dict

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# {'name': 'John'} { ' n a m e ' :   '
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v = str(object={'name':'John'}.keys()) # dict.keys()

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# dict_keys(['name']) d i c t _ k e y s (
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v = str(object={'name':'John'}.values()) # dict.values()

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# dict_values(['John']) d i c t _ v a l u e
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v = str(object={'name':'John'}.items()) # dict.items()

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# dict_items([('name', 'John')]) d i c t _ i t e m s
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v = str(object=iter([1, 2, 3])) # iterator

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# <list_iterator object at 0x00000200F4715930> < l i s t _ i t e r
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v = str(object=range(1, 4)) # range

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# range(1, 4) r a n g e ( 1 ,   4
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v = str(object=lambda: 10) # function

print(v, v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7], v[8], v[9])
# <function <lambda> at 0x00000200F3EA8E00> < f u n c t i o n
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<Decode a byte string to a string>: 

print(str(object=b'', encoding='utf-8', errors='strict'))
print(str(encoding='utf-8', errors='strict'))
print(str(encoding='utf-8'))
print(str(errors='strict'))
# Nothing
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='utf-8')

print(b)
# b"L\xd1\x91\xd1\x82's g\xcf\x86!"

print(str(object=b, encoding='utf-8'))
# Lёт's gφ!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='utf-7')

print(b)
# b"L+BFEEQg's g+A8Y!"

print(str(object=b, encoding='utf-7'))
# Lёт's gφ!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='utf-16')

print(b)
# b"\xff\xfeL\x00Q\x04B\x04'\x00s\x00 \x00g\x00\xc6\x03!\x00"

print(str(object=b, encoding='utf-16'))
# Lёт's gφ!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='big5')

print(b)
# b"L\xc7\xce\xc7\xdb's g\xa3p!"

print(str(object=b, encoding='big5'))
# Lёт's gφ! (Let's go!)
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='ascii', errors='ignore')

print(b)
# b"L's g!"

print(str(object=b, encoding='ascii', errors='ignore'))
# L's g!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='ascii', errors='replace')

print(b)
# b"L??'s g?!"

print(str(object=b, encoding='ascii', errors='replace'))
# L??'s g?!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='ascii', errors='xmlcharrefreplace')

print(b)
# b"L&#1105;&#1090;'s g&#966;!"

print(str(object=b, encoding='ascii', errors='xmlcharrefreplace'))
# L&#1105;&#1090;'s g&#966;!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='ascii', errors='backslashreplace')

print(b)
# b"L\\u0451\\u0442's g\\u03c6!"

print(str(object=b, encoding='ascii', errors='backslashreplace'))
# L\u0451\u0442's g\u03c6!
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import codecs

def hashreplace_handler(x):
    return ((x.end - x.start) * '#', x.end)

codecs.register_error('hashreplace', hashreplace_handler)

v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='ascii', errors='hashreplace')

print(b)
# b"L##'s g#!"

print(str(object=b, encoding='ascii', errors='hashreplace'))
# L##'s g#!
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v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='ascii', errors='strict')
# UnicodeEncodeError: 'ascii' codec can't encode characters
# in position 1-2: ordinal not in range(128)
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import codecs

def hashreplace_handler(x):
    return ((x.end - x.start) * '#', x.end)

codecs.register_error('hashreplace', hashreplace_handler)

v = "Lёт's gφ!" # Let's go!

b = v.encode(encoding='utf-8', errors='strict')

print(b)
# b"L\xd1\x91\xd1\x82's g\xcf\x86!"

print(str(object=b, encoding='ascii', errors='ignore'))
# L's g!

print(str(object=b, encoding='ascii', errors='replace'))
# L����'s g��!

print(str(object=b, encoding='ascii', errors='backslashreplace'))
# L\xd1\x91\xd1\x82's g\xcf\x86!

print(str(object=b, encoding='ascii', errors='hashreplace'))
# L####'s g##!

print(str(object=b, encoding='ascii', errors='strict'))
# UnicodeDecodeError: 'ascii' codec can't decode byte 0xd1
# in position 1: ordinal not in range(128)

print(str(object=b, encoding='ascii', errors='xmlcharrefreplace'))
# TypeError: don't know how to handle UnicodeDecodeError in error callback
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