What loop methods are commonly used in Python development?

1.for loop

The for loop is usually used to traverse sequences (such as lists, tuples, strings) or other iterable objects, and is more efficient.

The execution time of the for loop is proportional to the sequence length, so when processing larger data sets, the for loop is more efficient.

For example, to traverse a list containing 1 million elements, the execution time of the for loop only takes a few seconds.

The basic syntax of a for loop is:

for value in sequence:
    statement(s)

Among them, value is each element in the sequence, sequence is the sequence that needs to be traversed, and statement(s) is the statement that needs to be executed in the loop body .

The for loop is suitable for scenarios where you need to traverse sequences or other iterable objects, such as:

• Traverse sequences such as lists, tuples, strings, etc.;

• Traverse dictionaries, collections and other iterable objects;

• Traverse each line of data in the file;

• Traverse network data, etc.

2.while loop

The while loop is suitable for scenarios where an operation needs to be performed repeatedly, but the specific number of executions is not known.

The execution efficiency of while loop is related to the number of loops, so when the number of loops is small, the efficiency of while loop is relatively high.

However, if the number of loops is too many, performance will decrease.

The basic syntax of while loop is:

while condition:
    statement(s)

Among them, condition is the loop condition, and statement(s) is the statement that needs to be executed in the loop body.

The while loop is suitable for scenarios where an operation needs to be performed repeatedly, but the specific number of executions is not known, for example:

• Read user input until the input is correct;

• Simulation games and other scenes that require continuous looping;

• Handle tasks that need to be performed repeatedly.

It should be noted that if the loop condition is always True, it will cause an infinite loop, so a break statement needs to be added to the loop body to jump out of the loop.

3.do-while loop

The do-while loop is a loop method that is not natively supported in Python, but it can be implemented through while loops and break statements.

The do-while loop is suitable for scenarios where the loop needs to be executed at least once.

The execution efficiency of the do-while loop is similar to that of the while loop and depends on the number of loops.

The basic syntax of do-while loop is:

while True:
    statement(s)
    if not condition:
        break

Among them, True means that the loop is executed at least once, statement(s) is the statement that needs to be executed in the loop body, and condition is the loop condition.

The do-while loop is suitable for scenarios where the loop needs to be executed at least once, for example:

Read the data in the file and process the data;

The processing requires at least Perform one-time tasks, etc.

It should be noted that a break statement needs to be added to the loop body to jump out of the loop.

4.for-else loop

The for-else loop is also a commonly used loop method in Python. It can execute some additional code after the for loop ends.

The execution efficiency of the for-else loop is similar to that of the for loop and depends on the length of the sequence.

The basic syntax of a for-else loop is:

for value in sequence:
    statement(s)
else:
    statement(s)

Among them, value is each element in the sequence, sequence is the sequence that needs to be traversed, and statement(s) is what needs to be executed in the loop body statement.

The for-else loop is suitable for scenarios where some additional code needs to be executed after the for loop ends, for example:

• After traversing the list, summarize and count the data Wait for operations;

• Close the file after traversing the data in the file, etc.

It should be noted that the code in the else statement will be executed only when the for loop ends normally.

If the break statement is used in a for loop to jump out of the loop, the code in the else statement will not be executed.

5.while-else loop

The while-else loop is similar to the for-else loop and is also used to execute some additional code after the loop ends.

The execution efficiency of while-else loop is similar to that of while loop, depending on the number of loops.

The basic syntax of while-else loop is:

while condition:
    statement(s)
else:
    statement(s)

Among them, condition is the loop condition, and statement(s) is the statement that needs to be executed in the loop body.

The while-else loop is suitable for scenarios where some additional code needs to be executed after the while loop ends, for example:

• Processes tasks that need to be executed repeatedly until the task is completed ;

• Handle tasks that need to be retried continuously until the task succeeds.

It should be noted that the code in the else statement will be executed only when the while loop ends normally.

If the break statement is used in the while loop to jump out of the loop, the code in the else statement will not be executed.

To sum up, different circulation methods are suitable for different scenarios and efficiency requirements. When programming, you need to choose the appropriate loop method according to specific needs.

If you need to traverse a sequence, you should use a for loop; if you need to perform an operation repeatedly but do not know the specific number of executions, you can use a while loop;

If you need to execute the loop at least once, You can use a do-while loop (implemented through a while loop and a break statement);

If you need to execute some additional code after the loop ends, you can use a for-else loop or while-else loop.

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