Python 重复字符串直到达到指定长度

Python被世界各地的不同人群用于不同的目的，例如网站开发、机器学习、数据科学和自动化执行不同的过程。在这篇文章中，我们将学习如何通过反复重复同一个字符串来增加字符串的长度，直到达到我们所需的长度为止。

重复字符串的不同方法

字符串乘法

在这种方法中，我们通过乘法运算来实现所需的长度。我们将提供一个特定的值，并将字符串乘以该值，以达到指定数量的字符。该方法的语法如下：

def repeat_string(data, length): # The input of the string is given along with the value of number of characters in the final string
    whole_string = length // len(data)  # The number of times the whole string will be written is found
    extra_characters = length % len(data)    # The number of times some additional characters will be added to achieve the number of characters is found

    final_string = data * whole_string + data[:extra_characters] # A new string is created by repeating the whole string and adding some additional characters to achieve the required length

    return final_string

示例

上述方法的示例如下：

def repeat_string(data, length): # The input of the string is given along with the value of number of characters in the final string
    whole_string = length // len(data)  # The number of times the whole string will be written is found
    extra_characters = length % len(data)    # The number of times some additional characters will be added to achieve the number of characters is found

    final_string = data * whole_string + data[:extra_characters] # A new string is created by repeating the whole string and adding some additional characters to achieve the required length

    return final_string
old_string = "Example" # The input of the string is given
final_length = 25  # The desired number of characters are specified

new_string = repeat_string(old_string, final_length) # The function is repeat_string is run
print(new_string)

输出

以上代码的输出将如下：

ExampleExampleExampleExam

While循环

在这个方法中，while循环将持续执行字符串，直到达到所需的长度并且语句为真。上述方法的语法如下：

def whole_string(data, length): # The input of the string is given along with the value of number of characters in the final string
    final_string = "" # A new empty string is created which have the repeated string

    while len(final_string) < length: # The Condition is provided to the loop to achieve the desired length 
        final_string += data

    final_string = final_string[:length]  # Remove all the undesired elements and make the string of the required length

    return final_string

示例

上述方法的示例如下：

def whole_string(data, length): # The input of the string is given along with the value of number of characters in the final string
    final_string = "" # A new empty string is created which have the repeated string

    while len(final_string) < length: # The Condition is provided to the loop to achieve the desired length 
        final_string += data

    final_string = final_string[:length]  # Remove all the undesired elements and make the string of the required length

    return final_string
old_string = "Example" # The input of the string is given
final_length = 25 # The desired length of the string is specified

new_string = whole_string(old_string, final_length) # The function whole_string is run 
print(new_string)  # The output of the desired length is displayed

输出

方法的输出如下：

ExampleExampleExampleExam

迭代工具

迭代工具用于高效地检查字符串中的每个元素。我们将使用迭代工具库中的一个函数来实现字符串的所需长度，并在达到所需长度后使用切片函数停止对字符串的复制。此方法的语法如下：

import itertools  # Do not forget to import itertools or else error might occur

def whole_string(data, length): # The input of the string is given along with the desired length of the string
    final_string = ''.join(itertools.islice(itertools.cycle(data), length)) #The itertools.cycle will help to repeat the string and the itertools.slice will stop the repeatation once the desired length is achieved 
    return final_string

示例

上述方法的示例如下：

import itertools  # Do not forget to import itertools or else error might occur

def whole_string(data, length): # The input of the string is given along with the desired length of the string
    final_string = ''.join(itertools.islice(itertools.cycle(data), length)) #The itertools.cycle will help to repeat the string and the itertools.slice will stop the repeatation once the desired length is achieved 
    return final_string
old_string = "Example" # The input of the string is given
final_length = 25 # The desired length of the string is specified

new_string = whole_string(old_string, final_length) # The function whole_string is run
print(new_string)  # The output of the desired length is displayed

输出

上述代码的输出将如下所示：

ExampleExampleExampleExam

列表推导式

此方法将检查字符串中的每个元素，然后创建一个新的字符串，其中的元素将重复出现，直到达到所需的长度。该方法的语法如下：

def whole_string(data, length): # The input of the string is given along with the required length of the string
    final_string = [char for char in data for _ in range(length // len(data) + 1)] # Each element of the string is checked and then they are repeated until desired length is achieved
    updated_string = ''.join(final_string[:length]) # Once the desired length is achieved the elements are joined together into 1

    return updated_string

示例

上述方法的示例如下：

def whole_string(data, length): # The input of the string is given along with the required length of the string
    final_string = [char for char in data for _ in range(length // len(data) + 1)] # Each element of the string is checked and then they are repeated until desired length is achieved
    updated_string = ''.join(final_string[:length]) # Once the desired length is achieved the elements are joined together into 1

    return updated_string
old_string = "Example"  #The input of the string is given
final_length = 25 # The desired length of the string is provided

new_string = whole_string(old_string, final_length) # The function whole_string is run
print(new_string) # The output having the desired length is displayed