Say goodbye to manual editing: How to quickly create an Ansible hosts file with Python?

In the field of automated operation and maintenance, Ansible is a very powerful tool that can help us manage and configure a large number of servers. In order for Ansible to effectively manage these servers, we need a hosts list file that defines the target hosts that Ansible wants to manage.

In actual applications, we may have a file containing a lot of server equipment ledger information, such as ip.txt, and we want to convert these IP addresses into the format of Ansible hosts list. This article will introduce how to use Python scripts to achieve this goal.

1. Scenario Description

Suppose we have an ip.txt file that contains a series of server IP addresses that need to be managed. These IP addresses may be scattered or continuous. We want to convert these IP addresses into the format of the Ansible hosts list so that Ansible can identify and manage these servers. Specifically, we want to achieve the following functions:

• Read the IP address in the ip.txt file.
• Sort the IP addresses.
• Combine consecutive IP address ranges into a single range representation, for example, 192.168.1.[100:105].
• Generates an Ansible hosts inventory file that contains the IP address or IP address range of each host, and the corresponding connection information such as username, password, and port number.

2. Implementation steps

1. Read IP address

First, we need to write a Python script to read the IP addresses in the ip.txt file. We can use Python's built-in function open() to open the file and use the readlines() method to read each line of the file. The following is a code example to read the IP address:

 def read_data_from_csv(file_path): data = [] with open(file_path, 'r') as file: reader = csv.DictReader(file) for row in reader: data.append(row) return data

2. Sort IP addresses

After reading the IP addresses, we need to sort them. Python's built-in function sorted() can easily sort a list. The following is a code example to sort the IP addresses:

 def sort_ips_in_group(grouped_data): for subnet, rows in grouped_data.items(): grouped_data[subnet] = sorted(rows, key=lambda x: ip_to_int(x['IP'])) return grouped_data def ip_to_int(ip): parts = list(map(int, ip.split('.'))) return (parts[0] << 24) + (parts[1] << 16) + (parts[2] << 8) + parts[3]

3. Merge consecutive IP address ranges

To merge consecutive IP address ranges into a single range representation, we can traverse the sorted list of IP addresses and check if each IP address is consecutive to the previous one. If so, merge them into a single range. Here is a code example for merging consecutive IP address ranges:

 def merge_ip_ranges(sorted_ips): merged_ranges = [] current_range_start = None current_range_end = None for ip in sorted_ips: if current_range_start isNone: current_range_start = ip current_range_end = ip elif int(ip.split('.')[-1]) == int(current_range_end.split('.')[-1]) + 1: current_range_end = ip else: if current_range_start == current_range_end: merged_ranges.append(f"{current_range_start}") else: merged_ranges.append(f"{current_range_start.split('.')[0]}.{current_range_start.split('.')[1]}.{current_range_start.split('.')[2]}.[{current_range_start.split('.')[-1]}:{current_range_end.split('.')[-1]}]") current_range_start = ip current_range_end = ip # 处理最后一个范围if current_range_start isnotNone: if current_range_start == current_range_end: merged_ranges.append(f"{current_range_start}") else: merged_ranges.append(f"{current_range_start.split('.')[0]}.{current_range_start.split('.')[1]}.{current_range_start.split('.')[2]}.[{current_range_start.split('.')[-1]}:{current_range_end.split('.')[-1]}]") return merged_ranges

4. Generate Ansible hosts list

To simplify IP address management, we can merge consecutive IP address ranges into a larger range. Specifically, we can traverse the sorted list of IP addresses and check whether each IP address is continuous with the previous one. If they are found to be continuous, we merge them together. The advantage of doing this is that it is not only convenient for subsequent management and use, but also allows us to organize them with each IP segment as the group name. Finally, we convert these merged IP address ranges into the format of the Ansible hosts list. Ansible hosts list files generally include host groups, host names or IP addresses, and related connection information. The following is a code example for generating an Ansible hosts list:

 def generate_ansible_hosts(grouped_data): ansible_hosts = [] added_ips = set() # 使用集合来存储已经添加的IP地址def add_ip_range(start, end): start_str = ip_to_str(start) end_str = ip_to_str(end) start_parts = start_str.split('.') end_parts = end_str.split('.') if start_parts[:3] == end_parts[:3]: if start == end: # 如果start 和end 相同，直接添加单个IP 地址ansible_hosts.append(start_str) else: # 合并相同的前三个部分ansible_hosts.append(f"{start_parts[0]}.{start_parts[1]}.{start_parts[2]}.[{start_parts[3]}:{end_parts[3]}]") else: ansible_hosts.append(f"{start_str}") for subnet, rows in grouped_data.items(): ifnot rows: continue# 跳过空的子网ansible_hosts.append(f"[{subnet}]") current_range_start = None current_range_end = None for row in rows: try: ip = row['IP'] ip_int = ip_to_int(ip) if ip_int notin added_ips: # 检查IP地址是否已经添加过if current_range_start isNone: current_range_start = ip_int current_range_end = ip_int elif ip_int == current_range_end + 1: current_range_end = ip_int else: add_ip_range(current_range_start, current_range_end) current_range_start = ip_int current_range_end = ip_int added_ips.add(ip_int) # 将IP地址添加到集合中elif current_range_start isNoneornot (current_range_start <= ip_int <= current_range_end): ansible_hosts.append(ip) except KeyError as e: print(f"Missing key in row data: {e}") continue if current_range_start isnotNone: add_ip_range(current_range_start, current_range_end) ansible_hosts.append(f"[{subnet}:vars]") try: ansible_hosts.append(f"ansible_ssh_user={rows[0]['Username']}") ansible_hosts.append(f"ansible_ssh_pass={rows[0]['Password']}") ansible_hosts.append(f"ansible_ssh_port={rows[0]['Port']}") except (KeyError, IndexError) as e: print(f"Error accessing vars for subnet {subnet}: {e}") continue ansible_hosts.append("") return ansible_hosts

3. Script usage demonstration

First, generate the test IP data through a script. The script is as follows:

 import random def generate_random_ip(subnet): """生成一个随机的IP地址""" parts = subnet.split('.') if len(parts) < 4: parts.extend(['0'] * (4 - len(parts))) parts[3] = str(random.randint(1, 254)) return'.'.join(parts) def generate_test_data(file_path, num_records): """生成测试数据并写入CSV文件""" with open(file_path, 'w') as file: file.write("IP,Port,Username,Password\n") for _ in range(num_records): subnet = random.choice(['192.168.31', '192.168.32', '192.168.33', '192.168.34']) ip = generate_random_ip(subnet) port = 10022 if subnet == "192.168.31": username = "root" password = "pass@123" elif subnet == "192.168.33": username = "root" password = "P@ssw0rd" else: username = "admin" password = "password" file.write(f"{ip},{port},{username},{password}\n") # 示例文件路径file_path = 'test_data.csv' num_records = 800 # 生成测试数据并写入文件generate_test_data(file_path, num_records)

After executing the above script, an IP data will be generated in the current directory. These IP data are continuous and discontinuous. As shown in the following figure:

Then, by executing generate_ansible_hosts.py, you can generate the following results:

IV. Conclusion

Through the above steps, we have successfully used Python script to convert the ip.txt file into an Ansible hosts list. This script can help us automatically generate Ansible hosts lists and improve operation and maintenance efficiency. In actual applications, we can further expand and optimize the script as needed, such as supporting more connection information, processing IP addresses in different formats, etc. I hope this article is helpful to you. If you have any questions or suggestions, please leave a message for discussion.

5. How to obtain the script

The above scripts have been uploaded to gitee. You can get them if you need them. The repository on gitee mainly shares some commonly used scripts in work. You can frok or watch the repository so that you can pay attention to updates in time.

Warehouse address: https://gitee.com/didiplus/script