Python uses statements to control the flow of a program. These include assigning values to variables, making decisions with if, repeating code with loops (for, while), handling errors with try, defining functions and classes, and more. A key feature is dynamic typing, meaning a variable can hold any type of data (like a number, then text) without you having to declare its type first.

Python has below statements.

  • The assignment statement, using a single equals sign =
  • The if statement, which conditionally executes a block of code, along with else and elif (a contraction of else if)
  • The for statement, which iterates over an iterable object, capturing each element to a variable for use by the attached block; the variable is not deleted when the loop finishes
  • The while statement, which executes a block of code as long as boolean condition is true
  • The try statement, which allows exceptions raised in its attached code block to be caught and handled by except clauses (or new syntax except* in Python 3.11 for exception groups);[85] the try statement also ensures that clean-up code in a finally block is always run regardless of how the block exits
  • The raise statement, used to raise a specified exception or re-raise a caught exception
  • The class statement, which executes a block of code and attaches its local namespace to a class, for use in object-oriented programming
  • The def statement, which defines a function or method
  • The with statement, which encloses a code block within a context manager, allowing resource-acquisition-is-initialization (RAII)-like behavior and replacing a common try/finally idiom[86] Examples of a context include acquiring a lock before some code is run, and then releasing the lock; or opening and then closing a file
  • The break statement, which exits a loop
  • The continue statement, which skips the rest of the current iteration and continues with the next
  • The del statement, which removes a variable—deleting the reference from the name to the value, and producing an error if the variable is referred to before it is redefined [c]
  • The pass statement, serving as a NOP (i.e., no operation), which is syntactically needed to create an empty code block
  • The assert statement, used in debugging to check for conditions that should apply
  • The yield statement, which returns a value from a generator function (and also an operator); used to implement coroutines
  • The return statement, used to return a value from a function
  • The import and from statements, used to import modules whose functions or variables can be used in the current program
  • The match and case statements, analogous to a switch statement construct, which compares an expression against one or more cases as a control-flow measure

Now we will see the statements with some examples below

Assignment Statement (=)

The assignment statement (=) binds a variable name to a value as a reference to a separate, dynamically allocated object.

Python 
name = "Mithran"  # 'name' now refers to the string "Mithran"
age = 6        # 'age' now refers to the number 6

Conditional Statements (if, elif, else)

Executes code blocks based on conditions.

Python 
temperature = 25
if temperature > 30:
    print("It's hot!")
elif temperature > 20:
    print("It's pleasant.")  # This will be printed
else:
    print("It's cold.")

Loop Statements (for, while)

  • for: Iterates over items in a list, string, or other iterable.
Python 
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)
# Output:
# apple
# banana
# cherry
  • while: Repeats as long as a condition is true.
Python 
count = 3
while count > 0:
    print(count)
    count -= 1  # Decrease count by 1
# Output:
# 3
# 2
# 1

Loop Control (break, continue)

  • break: Exits the loop immediately.
Python 
for number in [1, 2, 3, 4, 5]:
    if number == 3:
        break
    print(number)
# Output:
# 1
# 2
  • continue: Skips the rest of the current iteration and moves to the next.
Python 
for number in [1, 2, 3, 4, 5]:
    if number == 3:
        continue
    print(number)
# Output:
# 1
# 2
# 4
# 5

Error Handling (try, except, finally)

Catches and handles exceptions (errors).

Python 
try:
    result = 10 / 0  # This will cause a ZeroDivisionError
except ZeroDivisionError:
    print("You can't divide by zero!")  # This is printed
finally:
    print("This always runs, error or not.")  # This is also printed

Function and Class Definition (def, class)

  • def: Defines a function.
Python 
def greet(name):
    return f"Hello, {name}!"

print(greet("Mithran"))  # Output: Hello, Mithran!
  • class: Defines a class for object-oriented programming.
Python 
class Dog:
    def __init__(self, name):
        self.name = name

    def bark(self):
        return "Woof!"

my_dog = Dog("Rocky")
print(my_dog.bark())  # Output: Woof!

Resource Management (with)

Ensures resources (like files) are properly closed after use.

Python 
# The file is automatically closed when the 'with' block ends.
with open('myfile.txt', 'r') as file:
    content = file.read()
    print(content)

Other Important Statements

  • del: Deletes a variable.
Python 
x = 100
del x  # The variable x is now gone
# print(x)  # This would cause a NameError
  • pass: A placeholder that does nothing.
Python 
def an_empty_function():
    pass  # We can't leave this blank, so we use 'pass'
  • assert: Checks if a condition is True; used for debugging.
Python 
x = 5
assert x > 0, "x should be positive"  # Nothing happens
# assert x < 0, "x should be negative"  # This would raise an AssertionError
  • yield: Returns a value from a generator function, pausing its state.
Python 
def count_up_to(n):
    count = 1
    while count <= n:
        yield count  # Pauses here and returns the value
        count += 1

for num in count_up_to(3):
    print(num)
# Output:
# 1
# 2
# 3
  • return: Exits a function and returns a value.
Python 
def add(a, b):
    return a + b

result = add(2, 3)  # result is now 5
  • import / from: Brings in code from other modules.
Python 
import math  # Import the entire math module
print(math.sqrt(16))  # Output: 4.0

from datetime import date  # Import only the 'date' class
today = date.today()
print(today)  # Output: 2023-10-27 (or today's date)
  • match / case (Python 3.10+): Like a powerful switch statement.
Python 
status_code = 404
match status_code:
    case 200:
        print("Success")
    case 404:
        print("Not Found")  # This will be printed
    case _:  # The default case
        print("Unknown status")
  • raise: Manually triggers an exception.
Python 
if some_condition_is_bad:
    raise ValueError("This is an error message")

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