Errors-Flow of control-Conditional statements-simple programs-Iterative Statement-Strings
- Syntax Errors:
- Violations of the rules of the programming language
(e.g., missing parentheses, incorrect indentation).
- Detected by the interpreter during the code
compilation.
- Logical Errors:
- Errors in the logic of the program that cause it to
produce incorrect results.
- Difficult to find as the program runs without
crashing.
- Runtime Errors:
- Errors that occur during the execution of the program.
- Example: ZeroDivisionError,
IndexError, TypeError.
Flow of Control
- Sequential Flow:
- Statements are executed in the order they appear in
the code.
- Conditional Flow:
- The flow of execution is determined by conditions.
- if, elif,
else statements are used to make decisions.
ifelifelse flow chart
- Iterative Flow:
- Statements are executed repeatedly.
- for loop: Iterates over a sequence (e.g., list, string).
- while loop: Executes as long as a condition is True.
while loop flow chart
Indentation
- Python uses indentation to define code blocks.
- Indentation is crucial for the correct execution of
conditional and iterative statements.
Certainly, let's delve into
Conditional Statements, Iterative Statements, Strings, and Lists in Python with
illustrative examples and images.
1. Conditional Statements
- if:
Executes a block of code only if a condition is True.
Python
if condition:
# code to be executed if condition
is True
- if-else:
Executes one block of code if a condition is True, and another block if
it's False.
Python
if condition:
# code to be executed if condition
is True
else:
# code to be executed if condition is False
if-elif-else: Allows for multiple conditions to be checked sequentially.
ifelifelse flowchart
Python
if
condition1:
# code to be executed if condition1 is True
elif
condition2:
# code to be executed if condition2 is True
else:
# code to be executed if none of the conditions are True
Example: Absolute Value
Python
num = int(input("Enter
a number: "))
if num >= 0:
absolute_value = num
else:
absolute_value = -num
print("Absolute value:", absolute_value)
Example: Sorting 3 Numbers
Python
num1
= int(input("Enter the first number: "))
num2
= int(input("Enter the second number: "))
num3
= int(input("Enter the third number: "))
if
num1 >= num2 and num1 >= num3:
largest = num1
if num2 >= num3:
middle = num2
smallest = num3
else:
middle = num3
smallest = num2
elif
num2 >= num1 and num2 >= num3:
largest = num2
if num1 >= num3:
middle = num1
smallest = num3
else:
middle = num3
smallest = num1
else:
largest = num3
if num1 >= num2:
middle = num1
smallest = num2
else:
middle = num2
smallest = num1
print("Sorted order:", smallest, middle, largest)
Example: Divisibility
Python
num = int(input("Enter
a number: "))
divisor = int(input("Enter
the divisor: "))
if num % divisor == 0:
print(num, "is divisible by", divisor)
else:
print(num, "is not divisible by", divisor)
2. Iterative Statements
- for loop:
Iterates over a sequence (e.g., list, string, range()).
Python
for item in sequence:
# code to be executed for each item
- range() function:
Generates a sequence of numbers.
- range(start, stop, step): Generates numbers from start (inclusive) to stop
(exclusive) with a specified step.
- while loop:
Executes as long as a condition is True.
Python
while condition:
# code to be executed as long as
condition is True
- break statement:
Exits the current loop prematurely.
- continue statement:
Skips the current iteration and moves to the next.
while loop flowchart
- Example: Generating Pattern
Python
for i in range(1, 6):
print("*" * i)
- Example: Summation of Series
Python
n = int(input("Enter
the number of terms: "))
sum = 0
for i in range(1, n+1):
sum += i
print("Sum of first", n, "natural numbers:", sum)
Example: Factorial of a Number
Python
num
= int(input("Enter a number: "))
factorial
= 1
if
num < 0:
print("Factorial is not defined for
negative numbers.")
elif
num == 0:
print("Factorial of 0 is 1")
else:
for i in range(1, num+1):
factorial *= i
print("Factorial
of", num, "is", factorial)
3. Strings
- Introduction:
A sequence of characters enclosed in single quotes (')
or double quotes (").
- String Operations:
- Concatenation:
Combining two or more strings using the +
operator.
- Repetition:
Repeating a string multiple times using the * operator.
- Membership:
Checking if a substring exists within a string using in and not
in.
- Slicing:
Extracting a portion of a string using indexing and slicing.
- Built-in Functions/Methods:
- len(): Returns the length of a string.
- capitalize(): Converts the first character to uppercase.
- title(): Converts the first character of each word to
uppercase.
- lower(): Converts all characters to lowercase.
- upper(): Converts all characters to uppercase.
- count(): Counts the number of occurrences of a substring.
- find(): Returns the index of the first occurrence of a substring.
- index(): Same as find(),
but raises an exception if the substring is not found.
- endswith(): Checks if the string ends with a specified suffix.
- startswith(): Checks if the string starts with a specified prefix.
- isalnum(): Checks if the string consists of alphanumeric
characters only.
- isalpha(): Checks if the string consists of only alphabetic
characters.
- isdigit(): Checks if the string consists of only digits.
- islower(): Checks if all characters are lowercase.
- isupper(): Checks if all characters are uppercase.
- isspace(): Checks if the string consists of only whitespace
characters.
- lstrip(): Removes leading whitespace characters.
- rstrip(): Removes trailing whitespace characters.
- strip(): Removes both leading and trailing whitespace
characters.
- replace(): Replaces occurrences of one substring with another.
- join(): Joins elements of a sequence with a string as a
separator.
- partition(): Splits the string at the first occurrence of a
specified separator.
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