📝 🏗️ Python Dictionaries

📝 🏗️ Python Dictionaries#

Python Dictionaries

📖 What Are Dictionaries?#

Definition: A dictionary in Python is a collection of key-value pairs, defined using curly braces {}. Keys are unique, and each key maps to a specific value.

Applications in Civil Engineering:

  • Storing material properties (e.g., density, strength)

  • Managing site data (e.g., location, project status)

  • Organizing project information (e.g., budgets, timelines)

🧱 Example: Material Properties#

Let’s create a dictionary to store properties of concrete:

# Material properties for concrete
concrete_properties = {
    "density": 2400,  # in kg/m³
    "compressive_strength": 30,  # in MPa
    "tensile_strength": 3.5,  # in MPa
}
print(concrete_properties)

{'density': 2400, 'compressive_strength': 30, 'tensile_strength': 3.5}

⚙️ Key Features of Dictionaries#

  1. Key-Value Pairs: Organize data for easy access.

  2. Dynamic: Add, modify, or remove key-value pairs as needed.

  3. Efficient: Quick lookups based on keys.

Example: Accessing and Modifying Data#

# Accessing a value
strength = concrete_properties["compressive_strength"]
print(f"Compressive Strength: {strength} MPa")

# Adding a new property
concrete_properties["modulus_of_elasticity"] = 25  # in GPa
print(concrete_properties)

Compressive Strength: 30 MPa
{'density': 2400, 'compressive_strength': 30, 'tensile_strength': 3.5, 'modulus_of_elasticity': 25}

🔄 Dictionary Operations#

Common operations for managing dictionaries:

  • Adding/Updating: dictionary[key] = value

  • Removing: del dictionary[key]

  • Keys and Values: Use .keys() and .values() to access them.

Example:#

# Removing a property
del concrete_properties["tensile_strength"]
print(concrete_properties)

# Listing all keys
print(concrete_properties.keys())

{'density': 2400, 'compressive_strength': 30, 'modulus_of_elasticity': 25}
dict_keys(['density', 'compressive_strength', 'modulus_of_elasticity'])

🏗️ Real-World Application#

Store project data for a construction site:

# Project data
project_data = {
    "site_name": "Downtown Tower",
    "location": "City Center",
    "budget": 5000000,  # in USD
    "status": "In Progress",
}
print(project_data)

{'site_name': 'Downtown Tower', 'location': 'City Center', 'budget': 5000000, 'status': 'In Progress'}

Example Use Cases:#

  • Update the status as the project progresses.

  • Calculate remaining budget by adding new costs.

🔧 Common Dictionary Methods#

Here are a few important methods for working with dictionaries:

.keys()#

Returns all the keys in the dictionary.

concrete_properties = {"density": 2400, "compressive_strength": 30}
print(
    concrete_properties.keys()
)  # Output: dict_keys(['density', 'compressive_strength'])

dict_keys(['density', 'compressive_strength'])

.get()#

Retrieves the value for a specified key, returning a default value if the key is not found.

# Retrieve value with default fallback
modulus = concrete_properties.get("modulus_of_elasticity", "Not Specified")
print(modulus)  # Output: Not Specified

Not Specified

⚠️ Limitations of Dictionary Keys#

Keys Must Be Immutable#

Dictionary keys must be immutable types like strings, numbers, or tuples. Mutable types like lists cannot be used.

# This will raise an error
# invalid_dict = {["key"]: "value"}  # TypeError

Keys Must Be Unique#

If a key is repeated, the latest value overwrites the previous one.

# Example of overwriting
example = {"a": 1, "a": 2}
print(example)  # Output: {'a': 2}

{'a': 2}