Learn None and Binary Data | Cross-Type Interactions

Real programs handle missing values and binary data. Use None to mark “no value”, and bytes/bytearray for raw binary content. Know when each is appropriate and how to convert safely between text and bytes.

`None` for “No Value”

None is a single object meaning “nothing here”.


              1234567
            
result = None
email = None
print(result is None)  # True
print(email is None)   # True

if result is None:
    print("No result yet")

Use is None instead of truthiness checks, since 0 and "" are also falsey.


              123
            
value = 0
print(not value)        # True
print(value is None)    # False

Defaults and Fallbacks


              1234567
            
x = None
print(x or "unknown")         # 'unknown'
print("unknown" if x is None else x)

x = 0
print(x or "unknown")         # 'unknown' (maybe wrong)
print("unknown" if x is None else x)  # 0

Functions and Parameters


              1234567
            
def add_tag(text, tag=None):
    if tag is None:
        tag = "general"
    return f"[{tag}] {text}"

print(add_tag("hello"))           # [general] hello
print(add_tag("hello", "news"))   # [news] hello

`bytes` and `bytearray` for Binary Data

str holds text; bytes and bytearray hold raw byte values.


              1234
            
b1 = b"hello"
b2 = bytes([72, 105])
buf = bytearray(b"abc")
buf[0] = 65

Encoding and Decoding


              123
            
text = "café"
data = text.encode("utf-8")
back = data.decode("utf-8")

Mixing Text and Bytes


              123456
            
try:
    b"ID:" + "123"
except TypeError as e:
    print(e)

ok = b"ID:" + "123".encode("utf-8")

Length Differences


              123
            
ch = "é"
len(ch)            # 1
len(ch.encode())   # 2

Files

# with open("example.png", "rb") as f:
#     blob = f.read()

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Section 4. Chapter 3

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`None` for “No Value”

None is a single object meaning “nothing here”.


              1234567
            
result = None
email = None
print(result is None)  # True
print(email is None)   # True

if result is None:
    print("No result yet")

Use is None instead of truthiness checks, since 0 and "" are also falsey.


              123
            
value = 0
print(not value)        # True
print(value is None)    # False

Defaults and Fallbacks


              1234567
            
x = None
print(x or "unknown")         # 'unknown'
print("unknown" if x is None else x)

x = 0
print(x or "unknown")         # 'unknown' (maybe wrong)
print("unknown" if x is None else x)  # 0

Functions and Parameters


              1234567
            
def add_tag(text, tag=None):
    if tag is None:
        tag = "general"
    return f"[{tag}] {text}"

print(add_tag("hello"))           # [general] hello
print(add_tag("hello", "news"))   # [news] hello

`bytes` and `bytearray` for Binary Data

str holds text; bytes and bytearray hold raw byte values.


              1234
            
b1 = b"hello"
b2 = bytes([72, 105])
buf = bytearray(b"abc")
buf[0] = 65

Encoding and Decoding


              123
            
text = "café"
data = text.encode("utf-8")
back = data.decode("utf-8")

Mixing Text and Bytes


              123456
            
try:
    b"ID:" + "123"
except TypeError as e:
    print(e)

ok = b"ID:" + "123".encode("utf-8")

Length Differences


              123
            
ch = "é"
len(ch)            # 1
len(ch.encode())   # 2

Files

# with open("example.png", "rb") as f:
#     blob = f.read()

Everything was clear?

Thanks for your feedback!

Section 4. Chapter 3

None and Binary Data

None for “No Value”

Defaults and Fallbacks

Functions and Parameters

bytes and bytearray for Binary Data

Encoding and Decoding

Mixing Text and Bytes

Length Differences

Files

Awesome!

None and Binary Data

None for “No Value”

Defaults and Fallbacks

Functions and Parameters

bytes and bytearray for Binary Data

Encoding and Decoding

Mixing Text and Bytes

Length Differences

Files

`None` for “No Value”

`bytes` and `bytearray` for Binary Data

`None` for “No Value”

`bytes` and `bytearray` for Binary Data