# Python | sympy.lambdify() method

With the help of sympy.lambdify() method, we can convert a SymPy expression to an expression that can be numerically evaluated. lambdify acts like a lambda function, except it, converts the SymPy names to the names of the given numerical library, usually NumPy or math.

Syntax: lambdify(variable, expression, library)

Parameters:
variable – It is the variable in the mathematical expression.
expression – It is the mathematical expression which is converted into its respective name in the given library.
library – It is the Python library to which expression is to be converted into.

Returns: Returns a lambda function which can evaluate a mathematical expression.

Example #1:
In this example we can see that by using sympy.lambdify() method, we can get a lambda function from a mathematical expression.

 `# import sympy ` `from` `sympy ``import` `*`  ` `  `x ``=` `symbols(``'x'``) ` `expr ``=` `sin(x) ` `    `  `# Use sympy.lambdify() method ` `f ``=` `lambdify(x, expr, ``"math"``)  ` `   `  `print``(``"Using lambda function in SymPy to evaluate sin(90) : {}"``.``format``(f(``90``)))  `

Output:

`Using lambda function in SymPy to evaluate sin(90) : 0.893996663601`

Example #2:
We can pass a dictionary of sympy_name:numerical_function pair to use lambdify with numerical libraries that it does not know about.

 `# import sympy ` `from` `sympy ``import` `*`  ` `  `def` `squared(n) :  ` `    ``return` `n``*``*``2` ` `  `x ``=` `symbols(``'x'``) ` `expr ``=` `x``*``*``2` `    `  `# Use sympy.lambdify() method ` `f ``=` `lambdify(x, expr, {``"**"` `: squared})  ` `   `  `print``(``"Using lambda function in SymPy to evaluate squared function : {}"``.``format``(f(``10``)))  `

Output:

```Using lambda function in SymPy to evaluate squared function : 100
```

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