Learn None and Binary Data | Cross-Type Interactions

Real programs often deal with missing values and raw binary data. Use None to represent the absence of a value, and bytes or bytearray to handle binary content from files or networks. Learn when to use each and how to safely convert between text and bytes.

`None` for "No Value"

None is a single special object that means "nothing here".


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# Basic checks
result = None
email = None
print("result is None:", result is None)     # True
print("email is None:", email is None)       # True

# Identity checks are the reliable way
if result is None:
    print("No result yet")
if email is not None:
    print("Email present")
else:
    print("Email missing")

None is falsey, but so are 0 and "". Prefer is None when you truly mean "missing".


              123
            
value = 0
print("not value:", not value)               # True - but 0 is a valid value
print("value is None:", value is None)       # False - correctly distinguishes 0 from missing

Defaults and Fallbacks


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x = None
safe_or = x or "unknown"                     # replaces any falsey value
safe_none_only = "unknown" if x is None else x
print("x=None, x or 'unknown':", safe_or)            # 'unknown'
print("x=None, None-only fallback:", safe_none_only) # 'unknown'

x = 0
safe_or = x or "unknown"
safe_none_only = "unknown" if x is None else x
print("x=0, x or 'unknown':", safe_or)               # 'unknown' - maybe not desired
print("x=0, None-only fallback:", safe_none_only)    # 0 - preserves valid zero

Functions and Parameters


              12345678910111213
            
def find_user(name):
    # returns None if not found
    return None

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

user = find_user("Ada")
print("user is None:", user is None)         # True
print(add_tag("hello"))                      # "[general] hello"
print(add_tag("hello", tag="news"))          # "[news] hello"

`bytes` and `bytearray` for Binary Data

Text uses str and holds Unicode characters. Binary data uses bytes or bytearray and holds raw byte values 0-255.


              123456789
            
# Creating binary data
b1 = b"hello"                  # bytes literal
b2 = bytes([72, 105])          # b"Hi"
buf = bytearray(b"abc")        # mutable
buf[0] = 65                    # now b"Abc"

print("b1:", b1, type(b1))     # b'hello' <class 'bytes'>
print("b2:", b2, type(b2))     # b'Hi'    <class 'bytes'>
print("buf:", buf, type(buf))  # bytearray(b'Abc') <class 'bytearray'>

Coverting Text and Bytes: Encode and Decode


              1234567
            
text = "café"
data = text.encode("utf-8")        # to bytes
back = data.decode("utf-8")        # back to str

print("text:", text, type(text))   # café <class 'str'>
print("data:", data, type(data))   # b'caf\xc3\xa9' <class 'bytes'>
print("back:", back, type(back))   # café <class 'str'>

Mixing Text and Bytes - Invalid without Conversion


              123456789
            
# Non-valid operation with explicit error print
try:
    bad = b"ID:" + "123"           # bytes + str - not allowed
except TypeError as e:
    print("TypeError when mixing bytes and str:", e)

# Correct combination
ok = b"ID:" + "123".encode("utf-8")
print("combined bytes:", ok)        # b'ID:123'

Lengths can differ


              123
            
ch = "é"
print("len('é') as str:", len(ch))                 # 1 character
print("len('é' encoded):", len(ch.encode("utf-8")))# 2 bytes

Files

# Binary files yield bytes
# 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 special object that means "nothing here".


              12345678910111213
            
# Basic checks
result = None
email = None
print("result is None:", result is None)     # True
print("email is None:", email is None)       # True

# Identity checks are the reliable way
if result is None:
    print("No result yet")
if email is not None:
    print("Email present")
else:
    print("Email missing")

None is falsey, but so are 0 and "". Prefer is None when you truly mean "missing".


              123
            
value = 0
print("not value:", not value)               # True - but 0 is a valid value
print("value is None:", value is None)       # False - correctly distinguishes 0 from missing

Defaults and Fallbacks


              1234567891011
            
x = None
safe_or = x or "unknown"                     # replaces any falsey value
safe_none_only = "unknown" if x is None else x
print("x=None, x or 'unknown':", safe_or)            # 'unknown'
print("x=None, None-only fallback:", safe_none_only) # 'unknown'

x = 0
safe_or = x or "unknown"
safe_none_only = "unknown" if x is None else x
print("x=0, x or 'unknown':", safe_or)               # 'unknown' - maybe not desired
print("x=0, None-only fallback:", safe_none_only)    # 0 - preserves valid zero

Functions and Parameters


              12345678910111213
            
def find_user(name):
    # returns None if not found
    return None

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

user = find_user("Ada")
print("user is None:", user is None)         # True
print(add_tag("hello"))                      # "[general] hello"
print(add_tag("hello", tag="news"))          # "[news] hello"

`bytes` and `bytearray` for Binary Data

Text uses str and holds Unicode characters. Binary data uses bytes or bytearray and holds raw byte values 0-255.


              123456789
            
# Creating binary data
b1 = b"hello"                  # bytes literal
b2 = bytes([72, 105])          # b"Hi"
buf = bytearray(b"abc")        # mutable
buf[0] = 65                    # now b"Abc"

print("b1:", b1, type(b1))     # b'hello' <class 'bytes'>
print("b2:", b2, type(b2))     # b'Hi'    <class 'bytes'>
print("buf:", buf, type(buf))  # bytearray(b'Abc') <class 'bytearray'>

Coverting Text and Bytes: Encode and Decode


              1234567
            
text = "café"
data = text.encode("utf-8")        # to bytes
back = data.decode("utf-8")        # back to str

print("text:", text, type(text))   # café <class 'str'>
print("data:", data, type(data))   # b'caf\xc3\xa9' <class 'bytes'>
print("back:", back, type(back))   # café <class 'str'>

Mixing Text and Bytes - Invalid without Conversion


              123456789
            
# Non-valid operation with explicit error print
try:
    bad = b"ID:" + "123"           # bytes + str - not allowed
except TypeError as e:
    print("TypeError when mixing bytes and str:", e)

# Correct combination
ok = b"ID:" + "123".encode("utf-8")
print("combined bytes:", ok)        # b'ID:123'

Lengths can differ


              123
            
ch = "é"
print("len('é') as str:", len(ch))                 # 1 character
print("len('é' encoded):", len(ch.encode("utf-8")))# 2 bytes

Files

# Binary files yield bytes
# 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

Coverting Text and Bytes: Encode and Decode

Mixing Text and Bytes - Invalid without Conversion

Lengths can differ

Files

1. Which check correctly detects a missing value?

2. Which line correctly combines text with a bytes prefix?

3. Which statement is correct?

None and Binary Data

`None` for "No Value"

Defaults and Fallbacks

Functions and Parameters

`bytes` and `bytearray` for Binary Data

Coverting Text and Bytes: Encode and Decode

Mixing Text and Bytes - Invalid without Conversion

Lengths can differ

Files

1. Which check correctly detects a missing value?

2. Which line correctly combines text with a bytes prefix?

3. Which statement is correct?

None and Binary Data

None for "No Value"

Defaults and Fallbacks

Functions and Parameters

bytes and bytearray for Binary Data

Coverting Text and Bytes: Encode and Decode

Mixing Text and Bytes - Invalid without Conversion

Lengths can differ

Files

1. Which check correctly detects a missing value?

2. Which line correctly combines text with a bytes prefix?

3. Which statement is correct?

None and Binary Data

None for "No Value"

Defaults and Fallbacks

Functions and Parameters

bytes and bytearray for Binary Data

Coverting Text and Bytes: Encode and Decode

Mixing Text and Bytes - Invalid without Conversion

Lengths can differ

Files

1. Which check correctly detects a missing value?

2. Which line correctly combines text with a bytes prefix?

3. Which statement is correct?

`None` for "No Value"

`bytes` and `bytearray` for Binary Data

`None` for "No Value"

`bytes` and `bytearray` for Binary Data