How to call a Function N times in Python

# Table of Contents

1. Call a function N times in Python
2. Call a function N times using itertools.repeat()
3. Call a function N times using a list comprehension
4. Call a function N times and store the results in a list using a for loop
5. Call a function N times using map()
6. Call a function N times using a while loop

# Call a function N times in Python

To call a function N times:

1. Use the range() class to create a range object of length N.
2. Use a for loop to iterate over the range object.
3. Call the function on each iteration.

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def print_message(message):
    print(message)

number = 1

for _ in range(5):
    number = number * 2
    print_message('bobbyhadz.com')

print(number)  # 👉️ 32

We used a for loop to iterate over a range object N times.

The range() class is commonly used for looping a specific number of times in for loops and takes the following arguments:

If you only pass a single argument to the range() constructor, it is considered to be the value for the stop parameter.

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for n in range(5):
    print(n) # 👉️ 0 1 2 3 4

result = list(range(5))

# 👇️ [0, 1, 2, 3, 4]
print(result)

If values for the start and stop parameters are provided, the start value is inclusive, whereas the stop value is exclusive.

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result = list(range(1, 5))

# 👇️ [1, 2, 3, 4]
print(result)

On each iteration of the for loop, we call a function and reassign a variable.

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def print_message(message):
    print(message)

number = 1

for _ in range(5):
    number = number * 2
    print_message('bobbyhadz.com')

print(number)  # 👉️ 32

You can use this approach to perform any other action N times.

Alternatively, you can use the itertools.repeat() class.

# Call a function N times using itertools.repeat()

This is a three-step process:

1. Use the itertools.repeat() class to create an iterator of length N.
2. Use a for loop to iterate over the iterator.
3. Call the function on each iteration.

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from itertools import repeat


def print_message(message):
    print(message)

number = 1

for _ in repeat(None, 5):
    number = number * 2
    print_message('bobbyhadz.com')

print(number)  # 👉️ 32

The itertools.repeat() class takes an object and the number of times the object should be repeated as arguments.

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from itertools import repeat

# 👇️ ['x', 'x', 'x', 'x', 'x']
print(list(repeat('x', 5)))

The method returns an iterator containing the object repeated N times.

The itertools.repeat() class is a little faster than the range() class in this scenario because it doesn't have to create an int object on each iteration.

However, the difference in performance is negligible (~15%) for most applications.

# Call a function N times using a list comprehension

This is a two-step process:

1. Use a list comprehension to iterate over a range object with length N.
2. On each iteration, call the function and return the result.

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def my_function(number):
    return number * 5


results = [my_function(10) for _ in range(3)]
print(results)  # 👉️ [50, 50, 50]

We used a list comprehension to iterate over the range object.

On each iteration, we call the function and return the result.

# Call a function N times and store the results in a list using a for loop

You can also use a for loop to call a function N times and store the results in a list.

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def increment(num):
    return num + 100


results = []

for i in range(1, 6):
    results.append(increment(i))

print(results)  # 👉️ [101, 102, 103, 104, 105]

On each iteration of the for loop, we call the function and append the result to the list.

After the last iteration, the list contains the output of all of the function's invocations.

# Call a function N times using map()

You can also use the map() function to call a function N times.

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def increment(num):
    return num + 100


list_of_arguments = [1, 2, 3, 4, 5]

results = list(map(increment, list_of_arguments))

print(results)  # 👉️ [101, 102, 103, 104, 105]

The map() function takes a function and an iterable as arguments and calls the function with each item of the iterable.

We passed the increment function to map, so it gets called with each item from the list.

The last step is to use the list() class to convert the map object to a list.

# Call a function N times using a while loop

You can also use a while loop to call a function N times.

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def print_message(message):
    print(message)


n = 3

while n > 0:
    print_message('bobbyhadz.com')

    n -= 1

# bobbyhadz.com
# bobbyhadz.com
# bobbyhadz.com

We initialized the n variable to 3 and used a while loop to iterate for as long as the variable is greater than 0.

On each iteration, we call the print_message function and decrement the n variable.

Once the n variable is set to 0 or less than 0, the condition is no longer met and the while loop exits.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Call a Function by a String name in Python
• How to check if a variable is a Function in Python
• Get all arguments passed to a Function in Python
• Why does my function print None in Python [Solved]
• SyntaxError: cannot assign to function call here in Python