Python调试神器PySnooper

 

解放print()，最专业的模块做最专业的事，PySnooper一款牛逼的模块，话不多说直接上代码：

1.安装

pip install pysnooper

或者

conda install -c conda-forge pysnooper

2.测试

import pysnooper

@pysnooper.snoop()
def number_to_bits(number):
    if number:
        bits = []
        while number:
            number, remainder = divmod(number, 2)
            bits.insert(0, remainder)
        return bits
    else:
        return [0]

number_to_bits(6)

输出结果

Starting var:.. number = 6
15:29:11.327032 call         4 def number_to_bits(number):
15:29:11.327032 line         5     if number:
15:29:11.327032 line         6         bits = []
New var:....... bits = []
15:29:11.327032 line         7         while number:
15:29:11.327032 line         8             number, remainder = divmod(number, 2)
New var:....... remainder = 0
Modified var:.. number = 3
15:29:11.327032 line         9             bits.insert(0, remainder)
Modified var:.. bits = [0]
15:29:11.327032 line         7         while number:
15:29:11.327032 line         8             number, remainder = divmod(number, 2)
Modified var:.. number = 1
Modified var:.. remainder = 1
15:29:11.327032 line         9             bits.insert(0, remainder)
Modified var:.. bits = [1, 0]
15:29:11.327032 line         7         while number:
15:29:11.327032 line         8             number, remainder = divmod(number, 2)
Modified var:.. number = 0
15:29:11.327032 line         9             bits.insert(0, remainder)
Modified var:.. bits = [1, 1, 0]
15:29:11.327032 line         7         while number:
15:29:11.327032 line        10         return bits
15:29:11.327032 return      10         return bits
Return value:.. [1, 1, 0]

或者，如果您不想跟踪整个函数，可以将相关部分包装在一个with块中：

import pysnooper
import random

def foo():
    lst = []
    for i in range(10):
        lst.append(random.randrange(1, 1000))

    with pysnooper.snoop():
        lower = min(lst)
        upper = max(lst)
        mid = (lower + upper) / 2
        print(lower, mid, upper)

foo()

输出如下：

New var:....... i = 9
New var:....... lst = [681, 267, 74, 832, 284, 678, ...]
09:37:35.881721 line        10         lower = min(lst)
New var:....... lower = 74
09:37:35.882137 line        11         upper = max(lst)
New var:....... upper = 832
09:37:35.882304 line        12         mid = (lower + upper) / 2
74 453.0 832
New var:....... mid = 453.0
09:37:35.882486 line        13         print(lower, mid, upper)

3.其他用法

3.1 将日志输入到日志文件中

3.2  查看非局部变量的值：

@pysnooper.snoop(variables=('foo.bar', 'self.whatever'))

3.3  显示函数调用的snoop行：

@pysnooper.snoop(depth=2)

3.4    窥探指定前缀的行：

@pysnooper.snoop（prefix ='ZZZ'）

 3.5   展开值以查看其所有属性或列表/词典项：

3.6   在多线程应用程序上，识别输出中窥探的线程：

3.7   您还可以自定义对象的repr：

def large(l):
    return isinstance(l, list) and len(l) > 5

def print_list_size(l):
    return 'list(size={})'.format(len(l))

def print_ndarray(a):
    return 'ndarray(shape={}, dtype={})'.format(a.shape, a.dtype)

@pysnooper.snoop(custom_repr=((large, print_list_size), (numpy.ndarray, print_ndarray)))
def sum_to_x(x):
    l = list(range(x))
    a = numpy.zeros((10,10))
    return sum(l)

sum_to_x(10000)

You will get l = list(size=10000) for the list, and a = ndarray(shape=(10, 10), dtype=float64) for the ndarray. The custom_repr are matched in order, if one condition matches, no further conditions will be checked.