一元二次方程的解法有以下几种：公式法、因式分解法、配方法、求根公式法。

下面是使用Python代码实现一元二次方程的解法：

1. 公式法：

“`python
import math

def solve_quadratic_equation(a, b, c):
    delta = b**2 – 4*a*c
    if delta < 0:
        return “无实根”
    elif delta == 0:
        x = -b / (2*a)
        return x
    else:
        x1 = (-b + math.sqrt(delta)) / (2*a)
        x2 = (-b – math.sqrt(delta)) / (2*a)
        return x1, x2

# 示例
a = 1
b = -3
c = 2
result = solve_quadratic_equation(a, b, c)
print(result)
“`

2. 因式分解法：

“`python
def solve_quadratic_equation(a, b, c):
    if a == 0:
        return “不是二次方程”
    if b == 0:
        x = 0
        if -c/a >= 0:
            return x, math.sqrt(-c/a)
        else:
            return “无实根”
    if c == 0:
        x1 = 0
        x2 = -b/a
        return x1, x2
    delta = b**2 – 4*a*c
    if delta < 0:
        return “无实根”
    elif delta == 0:
        x = -b / (2*a)
        return x
    else:
        x1 = (-b + math.sqrt(delta)) / (2*a)
        x2 = (-b – math.sqrt(delta)) / (2*a)
        return x1, x2

# 示例
a = 1
b = -3
c = 2
result = solve_quadratic_equation(a, b, c)
print(result)
“`

3. 配方法：

“`python
def solve_quadratic_equation(a, b, c):
    if a == 0:
        return “不是二次方程”
    if b == 0:
        x = 0
        if -c/a >= 0:
            return x, math.sqrt(-c/a)
        else:
            return “无实根”
    if c == 0:
        x1 = 0
        x2 = -b/a
        return x1, x2
    delta = b**2 – 4*a*c
    if delta < 0:
        return “无实根”
    elif delta == 0:
        x = -b / (2*a)
        return x
    else:
        x1 = (-b + math.sqrt(delta)) / (2*a)
        x2 = (-b – math.sqrt(delta)) / (2*a)
        return x1, x2

# 示例
a = 1
b = -3
c = 2
result = solve_quadratic_equation(a, b, c)
print(result)
“`

4. 求根公式法：

“`python
def solve_quadratic_equation(a, b, c):
    if a == 0:
        return “不是二次方程”
    if b == 0:
        x = 0
        if -c/a >= 0:
            return x, math.sqrt(-c/a)
        else:
            return “无实根”
    if c == 0:
        x1 = 0
        x2 = -b/a
        return x1, x2
    delta = b**2 – 4*a*c
    if delta < 0:
        return “无实根”
    elif delta == 0:
        x = -b / (2*a)
        return x
    else:
        x1 = (-b + math.sqrt(delta)) / (2*a)
        x2 = (-b – math.sqrt(delta)) / (2*a)
        return x1, x2

# 示例
a = 1
b = -3
c = 2
result = solve_quadratic_equation(a, b, c)
print(result)
“`

以上是四种常见的一元二次方程解法的Python代码实现。根据输入的系数a、b、c，可以得到方程的解或者无解的提示。