Lernen None- und Binärdaten | Interaktionen Zwischen Datentypen

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".


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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.


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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.


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

x = 0
print(x or "unknown")         # 'unknown'
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.


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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

Binary Data

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


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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.


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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.


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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.


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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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