Kinh Nghiệm Hướng dẫn How to return to a previous loop in python Mới Nhất
You đang tìm kiếm từ khóa How to return to a previous loop in python được Update vào lúc : 2022-09-27 00:40:28 . Với phương châm chia sẻ Kinh Nghiệm Hướng dẫn trong nội dung bài viết một cách Chi Tiết Mới Nhất. Nếu sau khi Read nội dung bài viết vẫn ko hiểu thì hoàn toàn có thể lại Comments ở cuối bài để Mình lý giải và hướng dẫn lại nha.
Try nesting the first while loop inside of the second. It’ll run your calculation code first, check to see if you’d like to do another, and then return to the top of the while True: loop to do another calculation.
Nội dung chính
- Using break
- Using continue
- break and continue visualized
- Using break and continue in nested loops.
- Loop Control in while loops
- Loops and the return statement
- How do you go back a loop in Python?
- How do you call a former loop in Python?
- How do you go back to a specific line in Python?
- Can you return a for loop?
Like this:
while True:
x, y = raw_input(“Enter 2 numbers separated by a space.”).split()
answer = 0
#Enter the 2 numbers to be calculated.
print “You have selected, A = “+ x + ” and B = ” + y + “.”
while int(y):
if (not int(y) % 2 == 0):
# this checks if y is even or odd
answer = int(answer) + int(x)
print “A = ” + str(x) + ” and B = ” + str(y) + “.”
print “B is odd so we’ll add A to the total.”
print “The running total is ” + str(answer) + “.”
else: (int(y) % 2 == 0)
print “A = ” + str(x) + ” and B = ” + str(y) + “.”
print “B is even, so we’ll ignore that number.”
x = int(x) * 2
y = int(y) / 2
print “The product is ” + str(answer) + “.”
a = raw_input(“Would you like to make another calculation? Y or N”)
if str(a) == “Y” or str(a) == “y”:
continue
if str(a) == “N” or str(a) == “n”:
print “Thank you have a nice day!”
break
else:
print “Invalid entry. Ending program.”
break
Hope that helps
Depending on what you’re trying to do, and where this particular code appears in your program, it’s usually advised to wrap your code inside of functions. That way, it doesn’t automatically run when you import
your module. You have to call a function to make the code run.
If you want to make this an executable script, you’d want to wrap the main loop code in a if __name__ == ‘__main__: block so that it only executes if it’s being executed directly.
e.g.:
def perform_calculation():
while True:
x, y = raw_input(“Enter 2 numbers separated by a space.”).split()
answer = 0
#Enter the 2 numbers to be calculated.
print “You have selected, A = “+ x + ” and B = ” + y + “.”
while int(y):
if (not int(y) % 2 == 0):
# this checks if y is even or odd
answer = int(answer) + int(x)
print “A = ” + str(x) + ” and B = ” + str(y) + “.”
print “B is odd so we’ll add A to the total.”
print “The running total is ” + str(answer) + “.”
else: (int(y) % 2 == 0)
print “A = ” + str(x) + ” and B = ” + str(y) + “.”
print “B is even, so we’ll ignore that number.”
x = int(x) * 2
y = int(y) / 2
print “The product is ” + str(answer) + “.”
def run_loop():
while True:
perform_calculation()
a = raw_input(“Would you like to make another calculation? Y or N”)
if str(a) == “Y” or str(a) == “y”:
continue
if str(a) == “N” or str(a) == “n”:
print “Thank you have a nice day!”
break
else:
print “Invalid entry. Ending program.”
break
if __name__ == ‘__main__’:
run_loop()
break and continue allow you to control the flow of your loops. They’re a concept that beginners to Python tend to misunderstand, so pay careful attention.
Using break
The break statement will completely break out of the current loop, meaning it won’t run any more of the statements contained inside of it.
>>> names = [“Rose”, “Max”, “Nina”, “Phillip”]
>>> for name in names:
… print(f”Hello, name”)
… if name == “Nina”:
… break
…
Hello, Rose
Hello, Max
Hello, Nina
break completely breaks out of the loop.
Using continue
continue works a little differently. Instead, it goes back to the start of the loop, skipping over any other statements contained within the loop.
>>> for name in names:
… if name != “Nina”:
… continue
… print(f”Hello, name”)
…
Hello, Nina
continue continues to the start of the loop
break and continue visualized
What happens when we run the code from this Python file?
# Python file names.py
names = [“Jimmy”, “Rose”, “Max”, “Nina”, “Phillip”]
for name in names:
if len(name) != 4:
continue
print(f”Hello, name”)
if name == “Nina”:
break
print(“Done!”)
Results
See if you can guess the results before expanding this section.
Using break and continue in nested loops.
Remember, break and continue only work for the current
loop. Even though I’ve been programming Python for years, this is something that still trips me up!
>>> names = [“Rose”, “Max”, “Nina”]
>>> target_letter=”x”
>>> for name in names:
… print(f”name in outer loop”)
… for char in name:
… if char == target_letter:
… print(f”Found name with letter: target_letter”)
… print(“breaking out of inner loop”)
… break
…
Rose in outer loop
Max in outer loop
Found Max with letter: x
breaking out of inner loop
Nina in outer loop
>>>
break in the inner loop only breaks out of the inner loop! The outer loop continues to run.
Loop Control in while loops
You can also use break and continue in while loops. One common scenario is running a loop forever, until a certain condition is met.
>>> count = 0
>>> while True:
… count += 1
… if count == 5:
… print(“Count reached”)
… break
…
Count reached
Be careful that your condition will
eventually be met, or else your program will get stuck in an infinite loop. For production use, it’s better to use asynchronous programming.
Loops and the return statement
Just like in functions, consider the return statement the hard kill-switch of the loop.
>>> def name_length(names):
… for name in names:
… print(name)
… if name == “Nina”:
… return “Found the special name”
…
>>> names = [“Max”, “Nina”, “Rose”]
>>> name_length(names)
Max
Nina
‘Found the special name’
How do you go back a loop in Python?
The continue statement in Python returns the control to the beginning of the while loop. The continue statement rejects all the remaining statements in the current iteration of the loop and moves the control back to the top of the loop. The continue statement can be used in both while and for loops.
How do you call a former loop in Python?
The following is a very common. use add line words = [] between print( … ) and option = …. Or you can add it to the top of the outer loop, b/c continue will send execution there before entering the inner loop.
How do you go back to a specific line in Python?
Python does not allow you to go back to a specific line number, and even if it did, you should not take advantage of that capability because it results in unmaintainable programs.
Can you return a for loop?
It is good practice to always have a return statement after the for/while loop in case the return statement inside the for/while loop is never executed. Otherwise, a compile-time error will occur because the method cannot return nothing (unless it has the Java reserved word “void” in the method header).
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