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Questions and Answers
What is a necessary part of the basic syntax for a for loop in Python?
What is a necessary part of the basic syntax for a for loop in Python?
What will be the output of the following code?
for i in range(3, 6):
print(i)
What will be the output of the following code?
for i in range(3, 6):
print(i)
What does the continue statement do in a for loop?
What does the continue statement do in a for loop?
How can you loop over the keys of a dictionary in Python using a for loop?
How can you loop over the keys of a dictionary in Python using a for loop?
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What happens when a break statement is executed inside a for loop?
What happens when a break statement is executed inside a for loop?
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How can a for loop iterate over a string in Python?
How can a for loop iterate over a string in Python?
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What will be printed by the following code?
for i in range(5):
if i == 3:
break
print(i)
What will be printed by the following code?
for i in range(5):
if i == 3:
break
print(i)
Signup and view all the answers
What is the purpose of the else clause in a for loop?
What is the purpose of the else clause in a for loop?
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Study Notes
Python for Loops
- A
forloop iterates over a sequence (e.g., list, tuple, string, range). - It executes a code block repeatedly for each item in the sequence.
Basic Syntax
-
forkeyword followed by a variable name. -
inkeyword. - The sequence to iterate over.
- Colon (
:) to start the code block. - Indentation for the code block.
Iterating over Lists
- Example iterating over a list of numbers:
numbers = [1, 2, 3, 4, 5]
for number in numbers:
print(number)
- Prints each number on a new line.
Iterating over Strings
- Strings are iterable sequences.
- Access each character:
my_string = "hello"
for character in my_string:
print(character)
Iterating with range()
- Loops a specific number of times.
-
range(start, stop, step)creates a sequence of numbers. Defaults torange(0, stop, 1). - Example looping 5 times:
for i in range(5):
print(i)
- Example looping from 2 to 5 with a step of 2:
for i in range(2, 6, 2):
print(i)
break Statement
- Terminates the loop prematurely.
- Used when a specific condition is met:
for i in range(10):
if i == 5:
break
print(i)
continue Statement
- Skips the rest of the code block in the current iteration, moving to the next.
for i in range(5):
if i == 2:
continue
print(i)
Nested Loops
- Loops placed inside another loop.
- Inner loop completes all iterations per outer loop iteration.
rows = 2
cols = 3
for row in range(rows):
for col in range(cols):
print(f"({row},{col})")
else Clause (with loops)
- Executes a code block when the loop completes normally (without
break).
for i in range(3):
print(i)
else:
print("Loop completed normally")
Looping over Dictionaries
- Dictionaries are iterable.
- Iteration by default is over the keys.
my_dict = {"a": 1, "b": 2, "c": 3}
for key in my_dict:
print(key)
## Access values:
for key in my_dict:
print(f"Key: {key}, Value: {my_dict[key]}")
Looping over enumerate
-
enumerate()function provides both index and value of an iterable.
my_list = ["apple", "banana", "cherry"]
for index, item in enumerate(my_list):
print(f"Index: {index}, Item: {item}")
Important Considerations
- Python's indentation is crucial.
- Ensure the sequence being iterated over is valid.
- Avoid infinite loops.
- Choose the correct loop type (e.g.,
forfor sequences,whilefor conditions).
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Description
This quiz covers the basics of 'for' loops in Python. You'll learn how to iterate over sequences like lists and strings, as well as how to use the 'range()' function for specific iterations. Test your understanding of syntax, structure, and practical applications of loops in Python programming.
