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From Python To C#

If you've done any programming before, it's likely you've used Python, as its popularity in schools as a first programming language has grown significantly in recent years. This section summarizes some of the key differences between Python and C# by comparing simple code snippets and highlighting key concepts.

Basic Syntax Comparison

Python Example

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# Python
userName = input("Enter your name > ")
print("Your name is ", userName)

C# Example

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using System;
namespace printName
{
    public class PrintName
    {
        static void Main(string[] args)
        {
            string userName;
            userName = Console.ReadLine();
            Console.WriteLine("Your name is " + userName);
        }
    }
}

Key Differences

  • Every C# program must define a class, and code is written inside that class.
  • Every variable and method must be assigned a data type.
  • The entry point for a C# program must be a method named Main().

The Python code can be structured similarly to C#:

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def main():
    userName = input("Enter your name > ")
    print("Your name is ", userName)

if __name__ == '__main__':
    main()

Notice in C#:

  • Every project will be in a namespace to organize code.
  • Curly braces { ... } define code blocks, unlike Python’s indentation.
  • Each statement ends with a semi-colon, ;.

Data Typing

Python is dynamically typed, meaning variable types are determined at runtime and can change during the program. C# is statically typed, meaning variable types are set before compilation and cannot change.

Example

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# Python
myVar = 5
myVar = "Hello"  # Now myVar is a string

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// C#
int myVar = 5;
// myVar = "Hello"; // Error: cannot assign a string to an int

In C#, you must declare variable types explicitly, and they cannot change type.

Comments

  • Single-line comments: Use //
  • Multi-line comments: Use /* ... */
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// This is a single-line comment
/* 
 * This is a multi-line comment 
 * spanning multiple lines
 */

Flow of Control

  • C# uses curly braces { ... } for code blocks instead of indentation.
  • Conditions must be enclosed in parentheses (...).
  • Use else if instead of elif.
  • C# includes a switch statement for multi-way branching.

Example

Python C#
if x > 0: if (x > 0) { ... }
elif x == 0: else if (x == 0) { ... }
for i in range(5): for (int i = 0; i < 5; i++) { ... }
for item in list: foreach (var item in list) { ... }

Boolean Expressions

  • C# uses true and false instead of True and False.
  • Boolean operators:
  • and -> &&
  • or -> ||
  • not -> !

Data Structures

  • C# arrays have fixed sizes, whereas List is used for dynamic sizes.
  • Lists in C# must specify the data type:
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List<int> numbers = new List<int>();
numbers.Add(5);

Classes

C# supports creating user-defined classes with their own properties and methods. It also supports inheritance and access modifiers.

Python

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class MyClass(BaseClass):
    def __init__(self, x):
        self.x = x

MyObject = MyClass(42)

C#

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class MyClass : BaseClass
{
    public MyClass(int x)
    {
        this.x = x;
    }
}
MyClass MyObject = new MyClass(42);

Access Modifiers

Modifier Visibility
public Accessible from anywhere
internal Accessible only within the project
protected Accessible within class and subclasses
private Accessible only within the class

Memory Management

C# uses garbage collection for automatic memory management. However, for non-memory resources like files or network connections, you should manually release them using the Dispose pattern or the using statement.

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using (StreamWriter writer = new StreamWriter("file.txt"))
{
    writer.WriteLine("Hello, World!");
}

In Python, this is similar to using the with statement.

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with open('file.txt', 'w') as writer:
    writer.write("Hello, World!")

Summary

Both Python and C# have their strengths and weaknesses. Understanding the differences in syntax, data types, and control structures will help you transition smoothly between these two languages.