str Comparison¶

Strings can be compared for equality and ordering.

Python compares strings lexicographically, character by character.

This is similar to dictionary ordering, but it is based on Unicode code points.

flowchart LR
    A[String A] --> C[character-by-character comparison]
    B[String B] --> C
    C --> D[Boolean result]
````

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## 1. Equality Comparison

Two strings are equal if they contain exactly the same characters in the same order.

```python
print("cat" == "cat")
print("cat" == "Cat")

Output:

True
False

String comparison is case-sensitive.

2. Inequality Comparison¶

print("cat" != "dog")

Output:

True

3. Ordering Comparison¶

Strings can be ordered with <, >, <=, and >=.

print("apple" < "banana")
print("cat" > "car")

Output:

True
True

Comparison proceeds from left to right until a differing character is found.

4. Case Matters¶

Uppercase and lowercase letters have different Unicode values.

print("Z" < "a")

This may produce a result that surprises beginners.

For user-facing comparisons, normalization is often needed.

print("Cat".lower() == "cat".lower())

Output:

True

5. Prefix Effects¶

Shorter strings can be smaller when one is a prefix of the other.

print("app" < "apple")

Output:

True

6. Worked Examples¶

Example 1: exact password check¶

password = "secret"
print(password == "secret")

Example 2: alphabetical order¶

print("ant" < "bat")

Example 3: case-insensitive comparison¶

a = "Python"
b = "python"

print(a.lower() == b.lower())

7. Common Pitfalls¶

Assuming comparisons ignore case¶

They do not unless you normalize explicitly.

Confusing human alphabetical order with Unicode order¶

Unicode-based comparison is precise, but not always what human sorting expects.

8. Summary¶

Key ideas:

• strings support equality and ordering comparisons
• comparisons are lexicographic
• case affects comparison results
• normalization is often needed for user-oriented comparisons

String comparison is essential in searching, sorting, validation, and conditional logic.