I want to get a subset of a dataframe based upon multiple conditions with the number of conditions I pass it variable. 

I have seen similar answers with multiple conditions([Select rows from a DataFrame based on values in a column in pandas](https://stackoverflow.com/questions/17071871/select-rows-from-a-dataframe-based-on-values-in-a-column-in-pandas))
, but none that allow to pass less variables. 

I have tried using: c=None, c=True, c=all, but it always evaluates to false

```py
def Subset (df, a=None, b=None, c=True): 
    temp=df.loc[(df['a'] == a) & (df['b'] == b) & (df['c'] == c)]

    return (temp)

```

if I evaluate: 

```
Subset=Subset(df=Table, a=350, b=300)

```

I get an empty dataframe

while if I use the function: 

```py
def Try(df, a=None, b=None): 
    temp=df.loc[(df['a'] == a) & (df['b'] == b)]

    return (temp)

```

I get a dataframe with 10 rows.

To answer Yaakov Bressler's comment I am giving more information: 
My dataframe looks like this: 

```
files,Names,Curve Type,Thickness,Temperature,Number,Iteration,leak,start,stop,Vth,F_E_M,on/off
Output [(1) _250-300-G21_]0.csv,250-300-G21,Output,250,300,G21,0,True,,,,,
Output [(1) _250-300-G22_]0.csv,250-300-G22,Output,250,300,G22,0,False,,,,,
Transfer lin [(1) _250-300-G21_;]0.csv,250-300-G21,Transfer lin,250,300,G21,0,True,,,,,

```

the first column are the filenames. the other columns are data about the transitor that file represents. 

I want to create a subset of this file representing a single transistor, defined by: ( Curve Type,Thickness,Temperature,Number ) or of a single chip : (Curve Type,Thickness,Temperature). 

This is so that I can import them and do plots/analysis.