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

None is used as a clear marker that a value is intentionally missing. It lets you distinguish between "no value provided" and valid values like 0 or "", making defaults and fallbacks safer and more predictable.


              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

This example shows how a function uses a parameter set to None as a signal that no tag was provided. It allows the function to assign a safe default while still letting the caller override it when needed.


              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

Encoding converts text into bytes so it can be stored or transferred reliably, while decoding restores those bytes back into readable text. Using a defined encoding like UTF-8 ensures characters are preserved correctly.


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

Mixing Text and Bytes

Text (str) and bytes (bytes) can't be combined directly because they represent different data types. To mix them safely, you must convert the text into bytes first using an explicit encoding.


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

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

Length Differences

Some characters take one text element but multiple bytes, so their length in str and in encoded form can differ. This happens because encodings like UTF-8 may use more than one byte to represent a single character.


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

Files

Binary files must be opened in "rb" mode so their raw bytes are read exactly as stored. This prevents Python from trying to interpret the data as text.

# 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

Text (str) and bytes (bytes) can't be combined directly because they represent different data types. To mix them safely, you must convert the text into bytes first using an explicit encoding.


              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

Binary files must be opened in "rb" mode so their raw bytes are read exactly as stored. This prevents Python from trying to interpret the data as text.

# 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

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